No,Category,Issue,Platform,Description,Do,Don't,Code Example Good,Code Example Bad,Severity
1,Navigation,Smooth Scroll,Web,Anchor links should scroll smoothly to target section,Use scroll-behavior: smooth on html element,Jump directly without transition,html { scroll-behavior: smooth; },<a href='#section'> without CSS,High
2,Navigation,Sticky Navigation,Web,Fixed nav should not obscure content,Add padding-top to body equal to nav height,Let nav overlap first section content,pt-20 (if nav is h-20),No padding compensation,Medium
3,Navigation,Active State,All,Current page/section should be visually indicated,Highlight active nav item with color/underline,No visual feedback on current location,text-primary border-b-2,All links same style,Medium
4,Navigation,Back Button,Mobile,Users expect back to work predictably,Preserve navigation history properly,Break browser/app back button behavior,history.pushState(),location.replace(),High
5,Navigation,Deep Linking,All,URLs should reflect current state for sharing,Update URL on state/view changes,Static URLs for dynamic content,Use query params or hash,Single URL for all states,Medium
6,Navigation,Breadcrumbs,Web,Show user location in site hierarchy,Use for sites with 3+ levels of depth,Use for flat single-level sites,Home > Category > Product,Only on deep nested pages,Low
7,Animation,Excessive Motion,All,Too many animations cause distraction and motion sickness,Animate 1-2 key elements per view maximum,Animate everything that moves,Single hero animation,animate-bounce on 5+ elements,High
8,Animation,Duration Timing,All,Animations should feel responsive not sluggish,Use 150-300ms for micro-interactions,Use animations longer than 500ms for UI,transition-all duration-200,duration-1000,Medium
9,Animation,Reduced Motion,All,Respect user's motion preferences,Check prefers-reduced-motion media query,Ignore accessibility motion settings,"// CSS: @media (prefers-reduced-motion: reduce) { * { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }}
// React hook:
const usePrefersReducedMotion = () => { const [prefersReduced, setPrefersReduced] = useState(false); useEffect(() => { const mq = window.matchMedia('(prefers-reduced-motion: reduce)'); setPrefersReduced(mq.matches); const handler = (e) => setPrefersReduced(e.matches); mq.addEventListener('change', handler); return () => mq.removeEventListener('change', handler); }, []); return prefersReduced; };
// Tailwind: motion-safe:animate-bounce motion-reduce:animate-none","// Ignores user preference: <div className=""animate-bounce"">Always animating</div>",High
10,Animation,Loading States,All,Show feedback during async operations,Use skeleton screens or spinners,Leave UI frozen with no feedback,"const Skeleton = () => (<div className=""animate-pulse space-y-4""><div className=""h-4 bg-gray-200 rounded w-3/4""></div><div className=""h-4 bg-gray-200 rounded w-1/2""></div><div className=""h-32 bg-gray-200 rounded""></div></div>); const Card = ({ isLoading data }) => isLoading ? <Skeleton /> : <div>{data}</div>;",Blank screen while loading,High
11,Animation,Hover vs Tap,All,Hover effects don't work on touch devices,Use click/tap for primary interactions,Rely only on hover for important actions,"// Good: Works on both touch and mouse
const Card = ({ onSelect, children }) => (<button onClick={onSelect} className=""p-4 border rounded-lg bg-white hover:bg-gray-50 active:bg-gray-100 focus:ring-2 focus:ring-blue-500 transition-colors touch-manipulation"">{children}</button>);
// For tooltips use click on mobile:
const Tooltip = ({ content, children }) => { const [show, setShow] = useState(false); return (<div className=""relative inline-block"" onMouseEnter={() => setShow(true)} onMouseLeave={() => setShow(false)} onClick={() => setShow(!show)}>{children}{show && <div className=""absolute z-10 p-2 bg-gray-900 text-white text-sm rounded"">{content}</div>}</div>);};","// Bad: Hover-only dropdown unreachable on touch
<div onMouseEnter={() => setOpen(true)}><Menu /></div>",High
12,Animation,Continuous Animation,All,Infinite animations are distracting,Use for loading indicators only,Use for decorative elements,animate-spin on loader,animate-bounce on icons,Medium
13,Animation,Transform Performance,Web,Some CSS properties trigger expensive repaints,Use transform and opacity for animations,Animate width/height/top/left properties,transform: translateY(),top: 10px animation,Medium
14,Animation,Easing Functions,All,Linear motion feels robotic,Use ease-out for entering ease-in for exiting,Use linear for UI transitions,ease-out,linear,Low
15,Layout,Z-Index Management,Web,Stacking context conflicts cause hidden elements,Define z-index scale system (10 20 30 50),Use arbitrary large z-index values,"// Define z-index scale in tailwind.config.js or CSS variables:
// z-0: base | z-10: dropdowns | z-20: sticky nav | z-30: modals | z-40: toasts | z-50: tooltips
const Modal = ({ children }) => (<div className=""fixed inset-0 z-30 flex items-center justify-center""><div className=""fixed inset-0 bg-black/50"" onClick={onClose} /><div className=""relative z-30 bg-white rounded-lg p-6 max-w-md w-full mx-4"">{children}</div></div>);
const Toast = ({ message }) => (<div className=""fixed bottom-4 right-4 z-40 p-4 bg-gray-900 text-white rounded-lg shadow-lg"">{message}</div>);","<div className=""z-[99999]"">Competing z-index</div> // Z-index wars cause bugs",High
16,Layout,Overflow Hidden,Web,Hidden overflow can clip important content,Test all content fits within containers,Blindly apply overflow-hidden,overflow-auto with scroll,overflow-hidden truncating content,Medium
17,Layout,Fixed Positioning,Web,Fixed elements can overlap or be inaccessible,Account for safe areas and other fixed elements,Stack multiple fixed elements carelessly,Fixed nav + fixed bottom with gap,Multiple overlapping fixed elements,Medium
18,Layout,Stacking Context,Web,New stacking contexts reset z-index,Understand what creates new stacking context,Expect z-index to work across contexts,Parent with z-index isolates children,z-index: 9999 not working,Medium
19,Layout,Content Jumping,Web,Layout shift when content loads is jarring,Reserve space for async content,Let images/content push layout around,"// Reserve space for images to prevent CLS (Cumulative Layout Shift)
<div className=""aspect-video bg-gray-100 rounded-lg overflow-hidden""><img src={imageUrl} alt=""..."" className=""w-full h-full object-cover"" loading=""lazy"" /></div>
// Skeleton with fixed dimensions:
const ImageSkeleton = () => (<div className=""aspect-video bg-gray-200 animate-pulse rounded-lg"" />);
// Next.js Image with placeholder:
<Image src=""/photo.jpg"" width={800} height={450} placeholder=""blur"" blurDataURL=""data:image/..."" className=""w-full h-auto"" />","<img src={url} /> // No dimensions causes layout shift when image loads",High
20,Layout,Viewport Units,Web,100vh can be problematic on mobile browsers,Use dvh or account for mobile browser chrome,Use 100vh for full-screen mobile layouts,min-h-dvh or min-h-screen,h-screen on mobile,Medium
21,Layout,Container Width,Web,Content too wide is hard to read,Limit max-width for text content (65-75ch),Let text span full viewport width,max-w-prose or max-w-3xl,Full width paragraphs,Medium
22,Touch,Touch Target Size,Mobile,Small buttons are hard to tap accurately,Minimum 44x44px touch targets,Tiny clickable areas,"<button className=""min-h-[44px] min-w-[44px] px-4 py-2 flex items-center justify-center bg-blue-600 text-white rounded-lg touch-manipulation"" aria-label=""Settings""><Settings className=""h-5 w-5"" /></button><a href=""/profile"" className=""inline-flex items-center min-h-[44px] px-3 py-2 text-blue-600 hover:underline"">View Profile</a>","<button className=""w-6 h-6 p-1""><Icon /></button> // 24px too small for touch",High
23,Touch,Touch Spacing,Mobile,Adjacent touch targets need adequate spacing,Minimum 8px gap between touch targets,Tightly packed clickable elements,gap-2 between buttons,gap-0 or gap-1,Medium
24,Touch,Gesture Conflicts,Mobile,Custom gestures can conflict with system,Avoid horizontal swipe on main content,Override system gestures,Vertical scroll primary,Horizontal swipe carousel only,Medium
25,Touch,Tap Delay,Mobile,300ms tap delay feels laggy,Use touch-action CSS or fastclick,Default mobile tap handling,touch-action: manipulation,No touch optimization,Medium
26,Touch,Pull to Refresh,Mobile,Accidental refresh is frustrating,Disable where not needed,Enable by default everywhere,overscroll-behavior: contain,Default overscroll,Low
27,Touch,Haptic Feedback,Mobile,Tactile feedback improves interaction feel,Use for confirmations and important actions,Overuse vibration feedback,navigator.vibrate(10),Vibrate on every tap,Low
28,Interaction,Focus States,All,Keyboard users need visible focus indicators,Use visible focus rings on interactive elements,Remove focus outline without replacement,"<button className=""px-4 py-2 bg-blue-600 text-white rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-2 transition-shadow"" onClick={handleClick}>Submit</button>","<button className=""outline-none"" onClick={handleClick}>Submit</button> // No visible focus indicator",High
29,Interaction,Hover States,Web,Visual feedback on interactive elements,Change cursor and add subtle visual change,No hover feedback on clickable elements,hover:bg-gray-100 cursor-pointer,No hover style,Medium
30,Interaction,Active States,All,Show immediate feedback on press/click,Add pressed/active state visual change,No feedback during interaction,active:scale-95,No active state,Medium
31,Interaction,Disabled States,All,Clearly indicate non-interactive elements,Reduce opacity and change cursor,Confuse disabled with normal state,opacity-50 cursor-not-allowed,Same style as enabled,Medium
32,Interaction,Loading Buttons,All,Prevent double submission during async actions,Disable button and show loading state,Allow multiple clicks during processing,"<button type=""submit"" disabled={isLoading} className=""px-4 py-2 bg-blue-600 text-white rounded-lg hover:bg-blue-700 disabled:opacity-50 disabled:cursor-not-allowed flex items-center gap-2""> {isLoading && <svg className=""animate-spin h-4 w-4"" viewBox=""0 0 24 24""><circle className=""opacity-25"" cx=""12"" cy=""12"" r=""10"" stroke=""currentColor"" strokeWidth=""4"" fill=""none""/><path className=""opacity-75"" fill=""currentColor"" d=""M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4z""/></svg>} {isLoading ? 'Submitting...' : 'Submit'}</button>","<button onClick={handleSubmit}>Submit</button> // Clickable during async operation",High
33,Interaction,Error Feedback,All,Users need to know when something fails,Show clear error messages near problem,Silent failures with no feedback,"<div className=""space-y-1""><input type=""email"" className={`w-full px-3 py-2 border rounded-lg ${error ? 'border-red-500 focus:ring-red-500' : 'border-gray-300 focus:ring-blue-500'} focus:outline-none focus:ring-2`} aria-invalid={!!error} aria-describedby={error ? 'email-error' : undefined} />{error && <p id=""email-error"" className=""text-sm text-red-600 flex items-center gap-1"" role=""alert""><AlertCircle className=""h-4 w-4"" />{error}</p>}</div>","<input type=""email"" /> // No error indication",High
34,Interaction,Success Feedback,All,Confirm successful actions to users,Show success message or visual change,No confirmation of completed action,Toast notification or checkmark,Action completes silently,Medium
35,Interaction,Confirmation Dialogs,All,Prevent accidental destructive actions,Confirm before delete/irreversible actions,Delete without confirmation,"<Dialog open={isOpen} onOpenChange={setIsOpen}><DialogContent className=""sm:max-w-md"" role=""alertdialog"" aria-labelledby=""dialog-title"" aria-describedby=""dialog-desc""><DialogHeader><DialogTitle id=""dialog-title"">Delete Item?</DialogTitle><DialogDescription id=""dialog-desc"">This action cannot be undone. This will permanently delete the item.</DialogDescription></DialogHeader><DialogFooter className=""flex gap-2""><Button variant=""outline"" onClick={() => setIsOpen(false)}>Cancel</Button><Button variant=""destructive"" onClick={handleDelete} className=""bg-red-600 hover:bg-red-700"">Delete</Button></DialogFooter></DialogContent></Dialog>","<button onClick={deleteItem}>Delete</button> // No confirmation",High
36,Accessibility,Color Contrast,All,Text must be readable against background,Minimum 4.5:1 ratio for normal text,Low contrast text,"<p className=""text-gray-900 dark:text-gray-100"">High contrast body text (21:1 ratio)</p><p className=""text-gray-700 dark:text-gray-300"">Secondary text (8.6:1 ratio)</p><span className=""text-lg font-semibold text-gray-800"">Large text 3:1 minimum</span>","<p className=""text-gray-400"">Low contrast gray text (2.8:1)</p> // Fails WCAG AA",High
37,Accessibility,Color Only,All,Don't convey information by color alone,Use icons/text in addition to color,Red/green only for error/success,"<div className=""flex items-center gap-2 text-red-600"" role=""alert""><XCircle className=""h-5 w-5"" aria-hidden=""true"" /><span>Error: Invalid email address</span></div><div className=""flex items-center gap-2 text-green-600""><CheckCircle className=""h-5 w-5"" aria-hidden=""true"" /><span>Success: Changes saved</span></div>","<div className=""border-red-500 border-2"">Error field</div> // Color only no text/icon",High
38,Accessibility,Alt Text,All,Images need text alternatives,Descriptive alt text for meaningful images,Empty or missing alt attributes,"<img src=""/hero.jpg"" alt=""Team collaborating around whiteboard in modern office"" className=""w-full h-auto rounded-lg"" /><figure><img src=""/chart.png"" alt="""" aria-describedby=""chart-desc"" className=""w-full"" /><figcaption id=""chart-desc"">Q3 revenue increased 25% compared to Q2</figcaption></figure>","<img src=""/photo.jpg"" /> // Missing alt attribute entirely",High
39,Accessibility,Heading Hierarchy,Web,Screen readers use headings for navigation,Use sequential heading levels h1-h6,Skip heading levels or misuse for styling,h1 then h2 then h3,h1 then h4,Medium
40,Accessibility,ARIA Labels,All,Interactive elements need accessible names,Add aria-label for icon-only buttons,Icon buttons without labels,"<button aria-label=""Close menu"" className=""p-2 rounded-full hover:bg-gray-100 focus:ring-2 focus:ring-blue-500"" onClick={onClose}><X className=""h-5 w-5"" aria-hidden=""true"" /></button><button aria-label=""Delete item"" aria-describedby=""delete-hint"" className=""p-2 text-red-600 hover:bg-red-50 rounded""><Trash2 className=""h-5 w-5"" aria-hidden=""true"" /></button><span id=""delete-hint"" className=""sr-only"">Permanently removes this item</span>","<button className=""p-2""><X className=""h-5 w-5"" /></button> // No accessible name",High
41,Accessibility,Keyboard Navigation,Web,All functionality accessible via keyboard,Tab order matches visual order,Keyboard traps or illogical tab order,"<div role=""toolbar"" aria-label=""Text formatting"" className=""flex gap-1""><button tabIndex={0} aria-pressed={isBold} onClick={toggleBold} className=""p-2 rounded hover:bg-gray-100 focus:ring-2 focus:ring-blue-500"">Bold</button><button tabIndex={0} onClick={toggleItalic} className=""p-2 rounded hover:bg-gray-100 focus:ring-2 focus:ring-blue-500"">Italic</button></div>// Use onKeyDown for arrow key navigation within toolbar","<div onClick={handleClick} className=""cursor-pointer"">Clickable div</div> // Not keyboard accessible",High
42,Accessibility,Screen Reader,All,Content should make sense when read aloud,Use semantic HTML and ARIA properly,Div soup with no semantics,<nav> <main> <article>,<div> for everything,Medium
43,Accessibility,Form Labels,All,Inputs must have associated labels,Use label with for attribute or wrap input,Placeholder-only inputs,"<div className=""space-y-2""><label htmlFor=""email"" className=""block text-sm font-medium text-gray-700"">Email address <span className=""text-red-500"" aria-hidden=""true"">*</span></label><input id=""email"" type=""email"" required aria-required=""true"" autoComplete=""email"" placeholder=""you@example.com"" className=""w-full px-3 py-2 border border-gray-300 rounded-lg focus:ring-2 focus:ring-blue-500 focus:border-blue-500"" /></div>","<input type=""email"" placeholder=""Email"" /> // Placeholder disappears on focus no persistent label",High
44,Accessibility,Error Messages,All,Error messages must be announced,Use aria-live or role=alert for errors,Visual-only error indication,"<div aria-live=""polite"" aria-atomic=""true"" className=""sr-only"">{announcement}</div><div role=""alert"" className=""p-4 bg-red-50 border border-red-200 rounded-lg flex items-start gap-3""><AlertCircle className=""h-5 w-5 text-red-600 flex-shrink-0 mt-0.5"" aria-hidden=""true"" /><div><p className=""font-medium text-red-800"">Form submission failed</p><p className=""text-sm text-red-700 mt-1"">Please correct the errors and try again.</p></div></div>","<div className=""border-red-500"">Error</div> // Not announced to screen readers",High
45,Accessibility,Skip Links,Web,Allow keyboard users to skip navigation,Provide skip to main content link,No skip link on nav-heavy pages,Skip to main content link,100 tabs to reach content,Medium
46,Performance,Image Optimization,All,Large images slow page load,Use appropriate size and format (WebP),Unoptimized full-size images,"import Image from 'next/image'; <Image src=""/hero.jpg"" alt=""Hero image"" width={800} height={400} priority className=""w-full h-auto"" sizes=""(max-width: 768px) 100vw (max-width: 1200px) 50vw 800px"" placeholder=""blur"" blurDataURL=""data:image/jpeg;base64...""/>// Or native: <img srcSet=""hero-400.webp 400w hero-800.webp 800w"" sizes=""(max-width: 600px) 400px 800px"" />","<img src=""/hero-4000px.jpg"" /> // Unoptimized 4000px image for 400px display",High
47,Performance,Lazy Loading,All,Load content as needed,Lazy load below-fold images and content,Load everything upfront,loading='lazy',All images eager load,Medium
48,Performance,Code Splitting,Web,Large bundles slow initial load,Split code by route/feature,Single large bundle,dynamic import(),All code in main bundle,Medium
49,Performance,Caching,Web,Repeat visits should be fast,Set appropriate cache headers,No caching strategy,Cache-Control headers,Every request hits server,Medium
50,Performance,Font Loading,Web,Web fonts can block rendering,Use font-display swap or optional,Invisible text during font load,font-display: swap,FOIT (Flash of Invisible Text),Medium
51,Performance,Third Party Scripts,Web,External scripts can block rendering,Load non-critical scripts async/defer,Synchronous third-party scripts,async or defer attribute,<script src='...'> in head,Medium
52,Performance,Bundle Size,Web,Large JavaScript slows interaction,Monitor and minimize bundle size,Ignore bundle size growth,Bundle analyzer,No size monitoring,Medium
53,Performance,Render Blocking,Web,CSS/JS can block first paint,Inline critical CSS defer non-critical,Large blocking CSS files,Critical CSS inline,All CSS in head,Medium
54,Forms,Input Labels,All,Every input needs a visible label,Always show label above or beside input,Placeholder as only label,"const FormField = ({ label, id, error, required, ...props }) => (<div className=""space-y-1.5""><label htmlFor={id} className=""block text-sm font-medium text-gray-700"">{label} {required && <span className=""text-red-500"">*</span>}</label><input id={id} aria-required={required} aria-invalid={!!error} aria-describedby={error ? `${id}-error` : undefined} className=""w-full px-3 py-2 border rounded-lg focus:ring-2 focus:ring-blue-500"" {...props} />{error && <p id={`${id}-error`} className=""text-sm text-red-600"">{error}</p>}</div>);","<input placeholder=""Email"" /> // Label disappears on input",High
55,Forms,Error Placement,All,Errors should appear near the problem,Show error below related input,Single error message at top of form,Error under each field,All errors at form top,Medium
56,Forms,Inline Validation,All,Validate as user types or on blur,Validate on blur for most fields,Validate only on submit,onBlur validation,Submit-only validation,Medium
57,Forms,Input Types,All,Use appropriate input types,Use email tel number url etc,Text input for everything,type='email',type='text' for email,Medium
58,Forms,Autofill Support,Web,Help browsers autofill correctly,Use autocomplete attribute properly,Block or ignore autofill,autocomplete='email',autocomplete='off' everywhere,Medium
59,Forms,Required Indicators,All,Mark required fields clearly,Use asterisk or (required) text,No indication of required fields,* required indicator,Guess which are required,Medium
60,Forms,Password Visibility,All,Let users see password while typing,Toggle to show/hide password,No visibility toggle,Show/hide password button,Password always hidden,Medium
61,Forms,Submit Feedback,All,Confirm form submission status,Show loading then success/error state,No feedback after submit,"const [status setStatus] = useState('idle'); // idle | loading | success | error
const handleSubmit = async (e) => { e.preventDefault(); setStatus('loading'); try { await submitForm(data); setStatus('success'); } catch { setStatus('error'); }};
<form onSubmit={handleSubmit}><button disabled={status === 'loading'} className=""px-4 py-2 bg-blue-600 text-white rounded-lg disabled:opacity-50"">{status === 'loading' ? 'Submitting...' : 'Submit'}</button>{status === 'success' && <p className=""text-green-600 flex items-center gap-2"" role=""status""><CheckCircle className=""h-4 w-4""/>Saved!</p>}{status === 'error' && <p className=""text-red-600"" role=""alert"">Failed. Try again.</p>}</form>","<button type=""submit"">Submit</button> // No loading/success/error feedback",High
62,Forms,Input Affordance,All,Inputs should look interactive,Use distinct input styling,Inputs that look like plain text,Border/background on inputs,Borderless inputs,Medium
63,Forms,Mobile Keyboards,Mobile,Show appropriate keyboard for input type,Use inputmode attribute,Default keyboard for all inputs,inputmode='numeric',Text keyboard for numbers,Medium
64,Responsive,Mobile First,Web,Design for mobile then enhance for larger,Start with mobile styles then add breakpoints,Desktop-first causing mobile issues,Default mobile + md: lg: xl:,Desktop default + max-width queries,Medium
65,Responsive,Breakpoint Testing,Web,Test at all common screen sizes,Test at 320 375 414 768 1024 1440,Only test on your device,Multiple device testing,Single device development,Medium
66,Responsive,Touch Friendly,Web,Mobile layouts need touch-sized targets,Increase touch targets on mobile,Same tiny buttons on mobile,"<nav className=""flex gap-1 md:gap-2""><a href=""/"" className=""min-h-[44px] md:min-h-[36px] px-4 py-3 md:py-2 text-sm font-medium rounded-lg hover:bg-gray-100 flex items-center"">Home</a><a href=""/about"" className=""min-h-[44px] md:min-h-[36px] px-4 py-3 md:py-2 text-sm font-medium rounded-lg hover:bg-gray-100 flex items-center"">About</a></nav>// Mobile: 44px height | Desktop: 36px height","<nav className=""flex gap-1""><a className=""px-2 py-1 text-xs"">Home</a></nav> // Same tiny size on all devices",High
67,Responsive,Readable Font Size,All,Text must be readable on all devices,Minimum 16px body text on mobile,Tiny text on mobile,"<p className=""text-base md:text-lg leading-relaxed text-gray-900"">Body text that scales responsively. Base 16px on mobile 18px on desktop.</p><span className=""text-sm text-gray-600"">Secondary text minimum 14px</span><input type=""text"" className=""text-base"" /> // Prevents iOS zoom on focus (16px+)","<p className=""text-xs leading-tight"">Tiny 12px body text</p> // Hard to read on mobile",High
68,Responsive,Viewport Meta,Web,Set viewport for mobile devices,Use width=device-width initial-scale=1,Missing or incorrect viewport,"<head><meta name=""viewport"" content=""width=device-width, initial-scale=1, viewport-fit=cover"" /><meta name=""theme-color"" content=""#3b82f6"" /></head>// Next.js: export const viewport = { width: 'device-width', initialScale: 1, viewportFit: 'cover' };","// No viewport meta - page renders at desktop width on mobile",High
69,Responsive,Horizontal Scroll,Web,Avoid horizontal scrolling,Ensure content fits viewport width,Content wider than viewport,"<main className=""w-full max-w-full overflow-x-hidden""><img className=""max-w-full h-auto"" src=""..."" alt=""..."" /><div className=""overflow-x-auto -mx-4 px-4 md:mx-0 md:px-0""><table className=""min-w-[600px] md:w-full"">...</table></div></main>// Allow horizontal scroll only for specific content like tables","<div className=""w-[1200px]"">Fixed width content</div> // Forces horizontal scroll on mobile",High
70,Responsive,Image Scaling,Web,Images should scale with container,Use max-width: 100% on images,Fixed width images overflow,max-w-full h-auto,width='800' fixed,Medium
71,Responsive,Table Handling,Web,Tables can overflow on mobile,Use horizontal scroll or card layout,Wide tables breaking layout,overflow-x-auto wrapper,Table overflows viewport,Medium
72,Typography,Line Height,All,Adequate line height improves readability,Use 1.5-1.75 for body text,Cramped or excessive line height,leading-relaxed (1.625),leading-none (1),Medium
73,Typography,Line Length,Web,Long lines are hard to read,Limit to 65-75 characters per line,Full-width text on large screens,max-w-prose,Full viewport width text,Medium
74,Typography,Font Size Scale,All,Consistent type hierarchy aids scanning,Use consistent modular scale,Random font sizes,Type scale (12 14 16 18 24 32),Arbitrary sizes,Medium
75,Typography,Font Loading,Web,Fonts should load without layout shift,Reserve space with fallback font,Layout shift when fonts load,font-display: swap + similar fallback,No fallback font,Medium
76,Typography,Contrast Readability,All,Body text needs good contrast,Use darker text on light backgrounds,Gray text on gray background,"<article className=""bg-white dark:bg-gray-900""><h1 className=""text-gray-900 dark:text-white font-bold text-2xl"">Heading</h1><p className=""text-gray-700 dark:text-gray-300 leading-relaxed"">Body text with 8:1+ contrast ratio for excellent readability.</p><span className=""text-gray-500 dark:text-gray-400 text-sm"">Caption text (4.5:1 minimum)</span></article>","<p className=""text-gray-400 bg-gray-100"">Low contrast text</p> // 2.5:1 ratio fails WCAG",High
77,Typography,Heading Clarity,All,Headings should stand out from body,Clear size/weight difference,Headings similar to body text,Bold + larger size,Same size as body,Medium
78,Feedback,Loading Indicators,All,Show system status during waits,Show spinner/skeleton for operations > 300ms,No feedback during loading,"const LoadingSpinner = ({ size = 'md' }) => (<svg className={`animate-spin ${size === 'sm' ? 'h-4 w-4' : 'h-6 w-6'} text-blue-600`} fill=""none"" viewBox=""0 0 24 24""><circle className=""opacity-25"" cx=""12"" cy=""12"" r=""10"" stroke=""currentColor"" strokeWidth=""4""/><path className=""opacity-75"" fill=""currentColor"" d=""M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4z""/></svg>);
const CardSkeleton = () => (<div className=""animate-pulse p-4 border rounded-lg""><div className=""h-4 bg-gray-200 rounded w-3/4 mb-4""/><div className=""h-20 bg-gray-200 rounded""/></div>);","// No loading indicator - UI appears frozen",High
79,Feedback,Empty States,All,Guide users when no content exists,Show helpful message and action,Blank empty screens,No items yet. Create one!,Empty white space,Medium
80,Feedback,Error Recovery,All,Help users recover from errors,Provide clear next steps,Error without recovery path,Try again button + help link,Error message only,Medium
81,Feedback,Progress Indicators,All,Show progress for multi-step processes,Step indicators or progress bar,No indication of progress,Step 2 of 4 indicator,No step information,Medium
82,Feedback,Toast Notifications,All,Transient messages for non-critical info,Auto-dismiss after 3-5 seconds,Toasts that never disappear,Auto-dismiss toast,Persistent toast,Medium
83,Feedback,Confirmation Messages,All,Confirm successful actions,Brief success message,Silent success,Saved successfully toast,No confirmation,Medium
84,Content,Truncation,All,Handle long content gracefully,Truncate with ellipsis and expand option,Overflow or broken layout,line-clamp-2 with expand,Overflow or cut off,Medium
85,Content,Date Formatting,All,Use locale-appropriate date formats,Use relative or locale-aware dates,Ambiguous date formats,2 hours ago or locale format,01/02/03,Low
86,Content,Number Formatting,All,Format large numbers for readability,Use thousand separators or abbreviations,Long unformatted numbers,"1.2K or 1,234",1234567,Low
87,Content,Placeholder Content,All,Show realistic placeholders during dev,Use realistic sample data,Lorem ipsum everywhere,Real sample content,Lorem ipsum,Low
88,Onboarding,User Freedom,All,Users should be able to skip tutorials,Provide Skip and Back buttons,Force linear unskippable tour,Skip Tutorial button,Locked overlay until finished,Medium
89,Search,Autocomplete,Web,Help users find results faster,Show predictions as user types,Require full type and enter,Debounced fetch + dropdown,No suggestions,Medium
90,Search,No Results,Web,Dead ends frustrate users,Show 'No results' with suggestions,Blank screen or '0 results',Try searching for X instead,No results found.,Medium
91,Data Entry,Bulk Actions,Web,Editing one by one is tedious,Allow multi-select and bulk edit,Single row actions only,Checkbox column + Action bar,Repeated actions per row,Low
92,AI Interaction,Disclaimer,All,Users need to know they talk to AI,Clearly label AI generated content,Present AI as human,"const AIMessage = ({ content timestamp }) => (<div className=""flex gap-3""><div className=""flex-shrink-0""><div className=""w-8 h-8 rounded-full bg-gradient-to-br from-purple-500 to-blue-500 flex items-center justify-center""><Sparkles className=""h-4 w-4 text-white"" /></div></div><div className=""flex-1""><div className=""flex items-center gap-2 mb-1""><span className=""font-medium text-gray-900"">AI Assistant</span><span className=""text-xs px-1.5 py-0.5 bg-purple-100 text-purple-700 rounded"">AI</span><time className=""text-xs text-gray-500"">{timestamp}</time></div><div className=""p-3 bg-gray-100 rounded-lg rounded-tl-none""><p className=""text-gray-800"">{content}</p></div><p className=""text-xs text-gray-500 mt-1 italic"">AI-generated content may contain errors</p></div></div>);","// Bad: <div><strong>Sarah</strong><p>{aiResponse}</p></div> // Fake human name hides AI",High
93,AI Interaction,Streaming,All,Waiting for full text is slow,Stream text response token by token,Show loading spinner for 10s+,Typewriter effect,Spinner until 100% complete,Medium
94,Spatial UI,Gaze Hover,VisionOS,Elements should respond to eye tracking before pinch,Scale/highlight element on look,Static element until pinch,hoverEffect(),onTap only,High
95,Spatial UI,Depth Layering,VisionOS,UI needs Z-depth to separate content from environment,Use glass material and z-offset,Flat opaque panels blocking view,.glassBackgroundEffect(),bg-white,Medium
96,Sustainability,Auto-Play Video,Web,Video consumes massive data and energy,Click-to-play or pause when off-screen,Auto-play high-res video loops,playsInline muted preload='none',autoplay loop,Medium
97,Sustainability,Asset Weight,Web,Heavy 3D/Image assets increase carbon footprint,Compress and lazy load 3D models,Load 50MB textures,Draco compression,Raw .obj files,Medium
98,AI Interaction,Feedback Loop,All,AI needs user feedback to improve,Thumps up/down or 'Regenerate',Static output only,Feedback component,Read-only text,Low
99,Accessibility,Motion Sensitivity,All,Parallax/Scroll-jacking causes nausea,Respect prefers-reduced-motion,Force scroll effects,@media (prefers-reduced-motion),ScrollTrigger.create(),High
100,Dashboard,KPI Hierarchy,Web,Dashboard KPIs should follow visual hierarchy,Most important KPIs largest and top-left,Equal sizing for all metrics,"const Dashboard = () => (<div className=""space-y-6""><div className=""grid grid-cols-1 md:grid-cols-2 gap-6""><KPICard title=""Total Revenue"" value=""$1.2M"" change=""+12%"" primary className=""md:col-span-2 p-6 bg-gradient-to-r from-blue-600 to-blue-700 text-white rounded-xl""/></div><div className=""grid grid-cols-2 md:grid-cols-4 gap-4"">{secondaryKPIs.map(kpi => (<KPICard key={kpi.id} {...kpi} className=""p-4 bg-white border rounded-lg"" />))}</div></div>);
const KPICard = ({ title value change primary className }) => (<div className={className}><p className={`text-sm ${primary ? 'text-blue-100' : 'text-gray-600'}`}>{title}</p><p className={`text-3xl font-bold ${primary ? 'text-white' : 'text-gray-900'}`}>{value}</p><span className=""text-sm text-green-500"">{change}</span></div>);","// All cards same size: <div className=""grid grid-cols-4 gap-4"">{kpis.map(k => <Card />)}</div>",High
101,Dashboard,Data Visualization Choice,Web,Choose chart types based on data story,Line for trends bar for comparison pie for composition,Wrong chart for data type,Line chart for time series,Pie chart for time series,High
102,Dashboard,Filter Persistence,Web,Dashboard filters should persist across sessions,Save filter state to localStorage or URL,Reset filters on page refresh,URL params for filter state,Filters reset on navigation,Medium
103,AI Interface,Streaming Response,All,AI responses should stream token by token,Show text as it generates with typing indicator,Wait for complete response then show,"const StreamingMessage = () => { const [text setText] = useState(''); const [isStreaming setIsStreaming] = useState(true);
useEffect(() => { const stream = await fetch('/api/ai' { method: 'POST' }).body.getReader();
while (true) { const { done value } = await stream.read(); if (done) break; setText(prev => prev + new TextDecoder().decode(value)); }
setIsStreaming(false); } []);
return (<div className=""prose""><p>{text}{isStreaming && <span className=""inline-block w-2 h-4 bg-gray-400 animate-pulse ml-1"" aria-label=""AI is typing"" />}</p></div>);};
// Shows text progressively as AI generates it","// Bad: 10+ second spinner then wall of text appears at once
<>{isLoading ? <Spinner /> : <p>{fullResponse}</p>}</>",High
104,AI Interface,Confidence Display,All,Show AI confidence levels when relevant,Visual confidence indicator for uncertain outputs,Hide uncertainty from users,Confidence bar or percentage,No indication of AI certainty,Medium
105,AI Interface,Error Recovery,All,AI errors should offer clear recovery paths,Retry button + alternative suggestions,Generic error message only,"const AIErrorState = ({ error onRetry onSimplify }) => (<div className=""p-4 bg-red-50 border border-red-200 rounded-lg"" role=""alert""><div className=""flex items-start gap-3""><AlertCircle className=""h-5 w-5 text-red-600 flex-shrink-0"" /><div className=""flex-1""><p className=""font-medium text-red-800"">Unable to generate response</p><p className=""text-sm text-red-700 mt-1"">{error.message || 'The AI service encountered an issue.'}</p><div className=""flex flex-wrap gap-2 mt-3""><button onClick={onRetry} className=""px-3 py-1.5 bg-red-600 text-white text-sm rounded-lg hover:bg-red-700 flex items-center gap-1""><RefreshCw className=""h-4 w-4"" />Try again</button><button onClick={onSimplify} className=""px-3 py-1.5 border border-red-300 text-red-700 text-sm rounded-lg hover:bg-red-100"">Simplify request</button></div></div></div></div>);","<p className=""text-red-600"">Error: Something went wrong</p> // No recovery options",High
106,WCAG 2.2,Target Size,All,Interactive elements need minimum 24x24px target,Minimum 24x24px (WCAG 2.5.8 AA),Smaller touch/click targets,"// WCAG 2.5.8 requires 24x24px minimum (AA) 44x44px for AAA
const IconButton = ({ icon: Icon label onClick }) => (<button onClick={onClick} aria-label={label} className=""min-w-[24px] min-h-[24px] p-1.5 rounded hover:bg-gray-100 focus:ring-2 focus:ring-blue-500 focus:outline-none inline-flex items-center justify-center""><Icon className=""h-4 w-4"" aria-hidden=""true"" /></button>);
// For mobile: use min-w-[44px] min-h-[44px] for better touch targets","<button className=""p-0.5""><X className=""h-3 w-3"" /></button> // 16px target too small",High
107,WCAG 2.2,Dragging Alternatives,All,Dragging operations need single-pointer alternative,Provide buttons or menus for drag actions,Drag-only interactions,"const ReorderItem = ({ item index onMove canMoveUp canMoveDown }) => (<li className=""flex items-center gap-2 p-3 bg-white border rounded-lg""><button aria-label=""Drag to reorder"" className=""cursor-grab p-1 hover:bg-gray-100 rounded""><GripVertical className=""h-5 w-5 text-gray-400"" /></button><span className=""flex-1"">{item.name}</span><div className=""flex flex-col""><button onClick={() => onMove(index -1)} disabled={!canMoveUp} aria-label=""Move up"" className=""p-1 hover:bg-gray-100 rounded disabled:opacity-30""><ChevronUp className=""h-4 w-4"" /></button><button onClick={() => onMove(index 1)} disabled={!canMoveDown} aria-label=""Move down"" className=""p-1 hover:bg-gray-100 rounded disabled:opacity-30""><ChevronDown className=""h-4 w-4"" /></button></div></li>);","// Drag-only: <div draggable onDrag={...}>{item}</div> // No keyboard alternative",High
108,Mobile UX,Gesture Patterns,Mobile,Use platform-native gesture patterns,Swipe to delete pull to refresh pinch to zoom,Custom unfamiliar gestures,iOS-style swipe actions,Custom swipe patterns,Medium
109,Mobile UX,Thumb Zone,Mobile,Place primary actions in thumb-friendly zones,Primary CTA bottom center or bottom right,Important actions at top of screen,"// Bottom navigation for primary actions - thumb-friendly zone
const MobileNav = () => (<nav className=""fixed bottom-0 inset-x-0 bg-white border-t safe-area-pb""><div className=""flex justify-around items-center h-16""><NavItem icon={Home} label=""Home"" href=""/"" /><NavItem icon={Search} label=""Search"" href=""/search"" /><NavItem icon={Plus} label=""Create"" href=""/new"" primary /><NavItem icon={Bell} label=""Alerts"" href=""/alerts"" /><NavItem icon={User} label=""Profile"" href=""/profile"" /></div></nav>);
// FAB for primary action: <button className=""fixed bottom-20 right-4 w-14 h-14 rounded-full bg-blue-600 shadow-lg"">+</button>","<header><button className=""absolute top-4 right-4"">+ Create</button></header> // Hard to reach with thumb",High
110,Voice UI,Multimodal Design,All,Voice interfaces should have visual fallbacks,Voice + screen + touch options,Voice-only with no visual,"const VoiceSearch = () => (<div className=""relative""><input type=""search"" placeholder=""Search or say a command..."" className=""w-full pl-10 pr-12 py-3 border rounded-lg"" aria-label=""Search"" /><Search className=""absolute left-3 top-1/2 -translate-y-1/2 h-5 w-5 text-gray-400"" /><button onClick={startVoice} aria-label={isListening ? 'Stop listening' : 'Start voice search'} className=""absolute right-2 top-1/2 -translate-y-1/2 p-2 rounded-full hover:bg-gray-100"">{isListening ? <MicOff className=""h-5 w-5 text-red-500 animate-pulse"" /> : <Mic className=""h-5 w-5 text-gray-600"" />}</button>{transcript && <p className=""mt-2 text-sm text-gray-600"" aria-live=""polite"">Heard: ""{transcript}""</p>}</div>);","// Voice-only: 'Say a command to continue' with no visual input option",High
111,Progressive Disclosure,AI Complexity,All,Hide AI complexity behind progressive disclosure,Simple default with advanced options expandable,All AI options visible at once,Advanced settings collapsed,20 AI parameters visible,Medium
112,Conversational UI,Thread Design,All,Chat threads need clear message attribution,Distinct visual separation between user and AI,Ambiguous message ownership,"const ChatMessage = ({ message isUser }) => (<div className={`flex gap-3 ${isUser ? 'flex-row-reverse' : ''}`}><div className=""flex-shrink-0""><div className={`w-8 h-8 rounded-full flex items-center justify-center ${isUser ? 'bg-blue-600' : 'bg-gray-200'}`}>{isUser ? <User className=""h-4 w-4 text-white"" /> : <Bot className=""h-4 w-4 text-gray-600"" />}</div></div><div className={`max-w-[80%] p-3 rounded-2xl ${isUser ? 'bg-blue-600 text-white rounded-br-md' : 'bg-gray-100 text-gray-900 rounded-bl-md'}`} aria-label={isUser ? 'You said' : 'Assistant said'}><p>{message.content}</p><time className={`text-xs mt-1 block ${isUser ? 'text-blue-200' : 'text-gray-500'}`}>{message.time}</time></div></div>);","// All messages same gray bubble - unclear who said what",High
113,Collaboration,Real-time Presence,Web,Show collaborator presence and activity,Cursor positions avatars typing indicators,No indication of other users,Live cursors with names,No presence indication,Medium
114,AI Systems,Graceful Degradation,All,AI features should degrade gracefully when unavailable,Fallback to non-AI alternative,Feature completely unavailable,"const SmartInput = ({ onSubmit }) => { const { data: suggestions error isLoading } = useAISuggestions(); return (<div className=""space-y-2""><div className=""relative""><input type=""text"" className=""w-full px-3 py-2 border rounded-lg pr-10"" placeholder=""Type or get AI suggestions..."" />{!error && <button onClick={getAISuggestion} disabled={isLoading} className=""absolute right-2 top-1/2 -translate-y-1/2 p-1 hover:bg-gray-100 rounded"" aria-label=""Get AI suggestion""><Sparkles className={`h-4 w-4 ${isLoading ? 'animate-pulse text-gray-400' : 'text-blue-600'}`} /></button>}</div>{error && <p className=""text-sm text-gray-500"">AI suggestions unavailable. Please type manually.</p>}{!error && suggestions && <SuggestionsList items={suggestions} />}</div>);};","// AI unavailable: <div className=""text-red-600"">Error: AI service is down</div> // Feature completely broken",High
115,Onboarding,AI Expectation Setting,All,Set realistic expectations for AI capabilities,Clear explanation of what AI can and cannot do,Overpromise AI capabilities,"const AIDisclaimer = () => (<div className=""p-4 bg-blue-50 border border-blue-200 rounded-lg""><div className=""flex items-start gap-3""><Info className=""h-5 w-5 text-blue-600 flex-shrink-0 mt-0.5"" /><div><h3 className=""font-medium text-blue-900"">About AI Assistant</h3><div className=""mt-2 text-sm text-blue-800 space-y-2""><p><strong>Can help with:</strong> Drafting content summarizing text answering questions brainstorming ideas</p><p><strong>Limitations:</strong> May produce inaccurate information. Cannot access real-time data or browse the web. Not suitable for medical legal or financial advice.</p><p className=""text-blue-600"">Always verify important information independently.</p></div></div></div></div>);","<p>AI can do anything you need!</p> // Overpromising leads to disappointment",High
116,Animation,View Transitions API,Web,Use View Transitions for smooth page-to-page navigation,Enable with startViewTransition() or CSS @view-transition,Instant jumps between pages without transition,"document.startViewTransition(() => { updateDOM(); }); // Or in CSS: @view-transition { navigation: auto; }","updateDOM(); // Direct DOM update without transition causes jarring page change",High
117,Animation,View Transition Names,Web,Named elements persist across page transitions with visual continuity,Add view-transition-name to shared elements like hero images,"Forget to name elements that should persist across views","<img src={hero} style={{ viewTransitionName: 'hero-image' }} alt=""Hero"" /> // Element morphs between pages","<img src={hero} alt=""Hero"" /> // No view-transition-name means no cross-page animation",Medium
118,Navigation,Cross-Document View Transitions,Web,Same-origin navigation transitions in Next.js/SPAs for seamless UX,Use Link with viewTransition prop in Next.js 15+,Ignore browser support - use progressive enhancement,"<Link viewTransition href=""/about"">About</Link> // Enables smooth cross-document transitions","<Link href=""/about"">About</Link> // No viewTransition prop means instant page swap",Medium
119,Animation,View Transition Fallback,Web,Handle browsers without View Transitions API support gracefully,Check document.startViewTransition support before using,Assume all browsers support View Transitions API,"if (document.startViewTransition) { document.startViewTransition(() => updateDOM()); } else { updateDOM(); } // Progressive enhancement","document.startViewTransition(() => updateDOM()); // Crashes in unsupported browsers",High
120,Animation,CSS Scroll-Driven Animations Basics,Web,Use animation-timeline: scroll() for scroll-linked animations,CSS animation-timeline: scroll(),JavaScript scroll event listeners,"animation-timeline: scroll(); animation-range: entry cover;","window.addEventListener('scroll', updateAnimation)",High
121,Animation,View Timeline for Element Visibility,Web,Use animation-timeline: view() for viewport-based animations,view() timeline for reveal animations,IntersectionObserver for simple reveals,"animation-timeline: view(); animation-range: entry 0% cover 40%;","useIntersectionObserver hook",Medium
122,Animation,Scroll-Driven Parallax Effects,Web,Create parallax without JavaScript using scroll(),CSS-only parallax with scroll timeline,requestAnimationFrame parallax,"@keyframes parallax { to { transform: translateY(-50%); } } .parallax { animation: parallax linear; animation-timeline: scroll(); }","onScroll={() => setTranslateY(scrollY * 0.5)}",Medium
123,Animation,Performance of Scroll Animations,Web,Prefer CSS scroll animations for better performance,CSS handles animation compositing,JS mutations every frame,".scroll-anim { animation: reveal linear; animation-timeline: scroll(); } /* Browser optimizes compositing */","requestAnimationFrame(() => element.style.transform = ...) // JS mutations every frame",High
124,Navigation,Navbar Scroll Threshold,Web,Navbar state should change at appropriate scroll distance,Use 50-100px scroll threshold for state change. Provides buffer before activating compact state,Change state immediately at scrollY > 0 (jarring) or too late > 150px (user misses transition),"window.addEventListener('scroll', () => { if (window.scrollY > 50) navbar.classList.add('scrolled'); else navbar.classList.remove('scrolled'); });","if (window.scrollY > 0) addClass('scrolled'); // Too sensitive triggers on any tiny scroll",Medium
125,Animation,Navbar Transition Timing,Web,Navbar transitions should feel smooth and professional,Use 0.3-0.4s duration with cubic-bezier easing for natural feel,Use linear easing or very fast transitions (<0.2s) which feel mechanical or jarring,".navbar { transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1); } .navbar-logo { transition: transform 0.3s ease; }",".navbar { transition: all 0.1s linear; } // Too fast and robotic",Medium
126,Navigation,Mobile Menu Animation Patterns,Mobile,Mobile menu should animate smoothly when opening and closing,Use max-height + opacity or transform for smooth open/close animations with proper easing,Use display:none toggle which provides no animation and feels abrupt,".mobile-nav { max-height: 0; opacity: 0; overflow: hidden; transition: max-height 0.35s ease, opacity 0.3s ease; } .mobile-nav.active { max-height: 400px; opacity: 1; }",".mobile-nav { display: none; } .mobile-nav.active { display: block; } // No animation just instant toggle",Medium
127,Performance,Image Loading Effects,Web,Use blur-up placeholder technique for smooth image loading experience,Use low-res blurred placeholder that transitions to full resolution image. Prevents layout shift and provides visual feedback,Show empty space or cause layout shift during image load. Avoid no visual feedback while loading,".img-lazy { filter: blur(10px); transition: filter 0.3s ease; } .img-lazy.loaded { filter: blur(0); } /* Or use placeholder: */ .img-container { background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%); background-size: 200% 100%; }","img { opacity: 0; } img.loaded { opacity: 1; } /* No visual feedback during load */",Medium
128,Performance,Content Loading Placeholder,Web,Use skeleton with shimmer animation for loading states to improve perceived performance,Use skeleton screens with shimmer animation that matches content layout. Provides visual feedback and reduces perceived wait time,Show spinner or empty area while loading. Avoid blocking UI with no indication of what will load,".skeleton { background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%); background-size: 200% 100%; animation: shimmer 1.5s infinite; border-radius: 4px; } @keyframes shimmer { 0% { background-position: -200% 0; } 100% { background-position: 200% 0; } } .skeleton-text { height: 1em; margin: 0.5em 0; } .skeleton-avatar { width: 48px; height: 48px; border-radius: 50%; }",".loading { content: 'Loading...'; } /* Or just empty div with no visual feedback */",Medium
129,Navigation,Header Height Transition,Web,Navbar should shrink height on scroll to maximize content viewport while maintaining accessibility,Shrink from 80px to 56px with smooth transition (0.3s ease-out). Use explicit height values not just padding changes. Transition should feel natural and not jarring,Keep navbar same height on scroll which wastes screen space. Shrink too fast (<0.2s) which feels mechanical. Use only padding changes without explicit height,".navbar { position: fixed; height: 80px; transition: height 0.3s ease-out padding 0.3s ease-out; } .navbar.scrolled { height: 56px; padding: 0.75rem 2rem; } /* CSS Scroll-Driven (2026): */ @supports (animation-timeline: scroll()) { .navbar { animation: shrink linear both; animation-timeline: scroll(root); animation-range: 0px 100px; } @keyframes shrink { from { height: 80px; } to { height: 56px; } } }",".navbar { height: 80px; } /* No scroll state - wastes 24px viewport space on long pages */",Medium
130,Navigation,Auto-Hide Navigation Direction,Web Mobile,Hide navbar on scroll down and show on scroll up for maximum content visibility on mobile and content-heavy pages,Track scroll direction using prevScrollY comparison. Hide with transform translateY(-100%) for GPU-accelerated animation. Add 80px threshold before hiding to prevent jitter. Use requestAnimationFrame for performance,Use display:none which provides no animation. Hide immediately on any scroll amount causing jittery UX. Use raw scroll events without requestAnimationFrame throttling,".navbar { transform: translateY(0); transition: transform 0.3s ease; } .navbar.hidden { transform: translateY(-100%); } /* JS: let prevScrollY = window.scrollY; let ticking = false; window.addEventListener('scroll' () => { if (!ticking) { requestAnimationFrame(() => { const currScrollY = window.scrollY; if (currScrollY > prevScrollY && currScrollY > 80) { navbar.classList.add('hidden'); } else if (currScrollY < prevScrollY) { navbar.classList.remove('hidden'); } prevScrollY = currScrollY; ticking = false; }); ticking = true; } }); */",".navbar { display: block; } .navbar.hidden { display: none; } /* No animation causes jarring UX. Also: hiding on any scroll without threshold */",Medium
