CSS11 min
How to Debug CSS Problems: A Practical Developer's Guide
Why your style isn't applying, what's causing the horizontal scrollbar, and how to work out which rule actually won. A methodical approach to CSS bugs.
Read article25 guides · 13 topicsGuides for people who
Guides for people who
debug things for a living
Practical write-ups on inspecting, debugging, testing and auditing websites. Written for developers, with the actual steps rather than the theory.
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SEO13 min
Technical SEO Checklist for Web Developers
The technical SEO work that belongs to developers: crawlability, indexing, canonicals, rendering, structured data and the checks to run before every release.
Read articlePerformance12 min
Website Performance Testing: A Practical Checklist for Developers
Measure the right things, in the right order: Core Web Vitals, payload weight, render-blocking assets, third-party scripts and the fixes that move the numbers.
Read articleAccessibility12 min
Web Accessibility Testing Checklist for Developers
The manual checks automated tools can't do, the ones they can, and how to test keyboard access, contrast, labels and screen reader output on a real page.
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HTML & DOM8 min
How to Validate HTML and CSS (and Fix What the Validator Finds)
Run the W3C HTML and CSS validators on any page, read the results in the right order, and fix the handful of mistakes that cause most of the errors.
Read articleAccessibility8 min
How to Check Color Contrast on a Website (WCAG AA and AAA)
What WCAG contrast ratios mean, how to measure them for any text on a page, how to simulate color blindness, and how to fix low-contrast designs without losing the brand.
Read articleCSS9 min
Debug CSS Layout Problems Fast with Outlines and Overlays
Outline every block, find the element causing horizontal scroll, see stacking order, and inspect flex and grid containers. A visual approach to the layout bugs that DevTools makes slow.
Read articleQA & Testing9 min
How to Test Web Forms Quickly: Validation, Labels and Edge Cases
A repeatable way to test any web form: fill it in seconds, break client-side validation on purpose, check labels and autocomplete, and confirm the server rejects what the browser should have caught.
Read articleSecurity7 min
How to Find and Fix Mixed Content Warnings on an HTTPS Site
Why an HTTPS page can still show as not fully secure, how to find every insecure image, script and stylesheet, and the fixes that stop mixed content for good.
Read articleSEO8 min
How to Check Meta Tags, Open Graph and Twitter Cards on Any Page
See exactly which title, description, canonical, robots and social tags a page sends, preview how it will look in search and when shared, and fix the mistakes that break link previews.
Read articleCSS7 min
How to Measure Elements on a Web Page (Size, Spacing and Alignment)
Measure widths, heights, margins and gaps on any website, line elements up against guides, and check a build against the design without screenshots and guesswork.
Read articleNetwork9 min
How to Check Redirects and HTTP Status Codes (and Fix Redirect Chains)
See every hop a URL takes, what each status code means for users and search engines, and how to fix redirect chains, loops and soft 404s after a migration.
Read articleJavaScript9 min
How to Debug JavaScript Errors in the Browser, Step by Step
Read console errors properly, find the line that threw, catch unhandled promise rejections, track down rogue event listeners and fix the five errors you'll see most.
Read articleDevTools8 min
How to Format, Validate and Compare JSON in Your Browser
Pretty-print unreadable API responses, find the exact character that breaks a JSON file, validate against a schema, compare two payloads and decode JWTs, without pasting data into random websites.
Read articleQA & Testing13 min
The Ultimate Website QA Checklist Before Launch
Everything worth checking before a site goes live, grouped by risk: the things that lose money, the things that lose traffic, and the things people notice.
Read articleDevTools11 min
Chrome DevTools Tips That Make Web Development Faster
Shortcuts, panels and console tricks that most developers never find, organised by the task you're trying to finish.
Read articlePerformance10 min
How to Analyze Images on a Web Page
Audit every image on a page: what it weighs, whether it's oversized for its slot, which format it should be in, and whether the alt text is doing its job.
Read articleSecurity12 min
Essential Website Security Checks Every Web Developer Should Know
Security headers, cookie flags, mixed content, exposed secrets and third-party risk: the front-end checks you can run on any page in a few minutes.
Read articleTech Stack9 min
How to Find What Technologies a Website Uses
Identify the framework, CMS, CDN, analytics and hosting behind any site by reading the signals it leaves in headers, markup, globals and network requests.
Read articleStorage10 min
How to Inspect Local Storage, Session Storage and Cookies in Chrome
Find, read, edit and clear client-side storage in Chrome, understand which mechanism to use for what, and debug the state bugs they cause.
Read articleQA & Testing9 min
How to Find Broken Links, Missing Images and Page Errors
Three kinds of rot that creep into every site, how to find each one quickly, and how to stop them coming back after the next release.
Read articleSEO13 min
Technical SEO Checklist for Web Developers
The technical SEO work that belongs to developers: crawlability, indexing, canonicals, rendering, structured data and the checks to run before every release.
Read articleAccessibility12 min
Web Accessibility Testing Checklist for Developers
The manual checks automated tools can't do, the ones they can, and how to test keyboard access, contrast, labels and screen reader output on a real page.
Read articlePerformance12 min
Website Performance Testing: A Practical Checklist for Developers
Measure the right things, in the right order: Core Web Vitals, payload weight, render-blocking assets, third-party scripts and the fixes that move the numbers.
Read articleResponsive10 min
How to Test Responsive Design Across Different Screen Sizes
A working method for responsive testing: which widths matter, what device emulation gets wrong, and the checks that catch real mobile bugs.
Read articleNetwork9 min
How to View HTTP Headers in Chrome
See request and response headers for any page or asset in Chrome, plus a reference for the headers that actually change how your site behaves.
Read articleJavaScript7 min
How to Disable JavaScript on a Website in Chrome
Turn JavaScript off for one site or all sites in Chrome, using settings, DevTools or a per-site toggle, and know which method fits which job.
Read articleCSS11 min
How to Debug CSS Problems: A Practical Developer's Guide
Why your style isn't applying, what's causing the horizontal scrollbar, and how to work out which rule actually won. A methodical approach to CSS bugs.
Read articleHTML & DOM9 min
How to Inspect and Debug HTML on Any Web Page
Open the inspector, read the DOM instead of the source, and track down the markup problems that cause layout, accessibility and SEO bugs.
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