html · chain · relay · step 021 of 64
offline render, Chrome 154, light scheme, 2 s of virtual time
runs in a sandboxed frame with no origin; live pages may fetch CDN fonts the offline render did not
<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<meta http-equiv="content-security-policy" content="default-src 'none'; style-src 'sha256-+xb7e3Yv0VTOgKaFnvEKGz9cFb9Tz9b9lxLJg8gR8Q='; img-src data:; base-uri 'none'; form-action 'none'">
<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
<meta name="description" content="A well-structured, accessible HTML5 document with modern best practices.">
<meta name="color-scheme" content="light dark">
<meta name="theme-color" content="#ffffff" media="(prefers-color-scheme: light)">
<meta name="theme-color" content="#121212" media="(prefers-color-scheme: dark)">
<meta name="author" content="ksmith@centricle.com">
<meta name="robots" content="index, follow">
<title>Welcome</title>
<link rel="icon" href="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'%3E%3Ctext y='.9em' font-size='90'%3E👋%3C/text%3E%3C/svg%3E">
<link rel="canonical" href="https://example.com/">
<meta property="og:type" content="website">
<meta property="og:title" content="Welcome">
<meta property="og:description" content="A well-structured, accessible HTML5 document with modern best practices.">
<meta property="og:url" content="https://example.com/">
<meta property="og:site_name" content="Welcome">
<meta property="og:image" content="https://example.com/og-image.png">
<meta property="og:image:width" content="1200">
<meta property="og:image:height" content="630">
<meta property="og:image:alt" content="Site preview image">
<meta property="og:locale" content="en_US">
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:title" content="Welcome">
<meta name="twitter:description" content="A well-structured, accessible HTML5 document with modern best practices.">
<meta name="twitter:image" content="https://example.com/og-image.png">
<meta name="twitter:image:alt" content="Site preview image">
<style>
:root {
color-scheme: light dark;
--text: #1a1a1a;
--text-secondary: #555;
--background: #fff;
--accent: #0052a3;
--border: #e0e0e0;
}
@media (prefers-color-scheme: dark) {
:root {
--text: #e0e0e0;
--text-secondary: #a0a0a0;
--background: #121212;
--accent: #5fa3ff;
--border: #333;
}
}
*,
*::before,
*::after {
box-sizing: border-box;
}
html {
-webkit-text-size-adjust: 100%;
text-size-adjust: 100%;
}
@media (prefers-reduced-motion: no-preference) {
html {
scroll-behavior: smooth;
}
a {
transition: text-decoration-thickness 0.15s ease;
}
.skip-link {
transition: transform 0.15s ease;
}
button {
transition: opacity 0.15s ease, transform 0.15s ease;
}
}
body {
display: grid;
grid-template-rows: auto 1fr auto;
min-height: 100vh;
min-height: 100dvh;
font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
font-size: 1rem;
line-height: 1.6;
max-width: 70ch;
margin: 0 auto;
padding: clamp(1rem, 5vw, 1.5rem);
padding-top: max(clamp(1rem, 5vw, 1.5rem), env(safe-area-inset-top));
padding-right: max(clamp(1rem, 5vw, 1.5rem), env(safe-area-inset-right));
padding-bottom: max(clamp(1rem, 5vw, 1.5rem), env(safe-area-inset-bottom));
padding-left: max(clamp(1rem, 5vw, 1.5rem), env(safe-area-inset-left));
color: var(--text);
background: var(--background);
}
h1 {
color: var(--accent);
font-size: clamp(1.75rem, 1.25rem + 3vw, 2.5rem);
font-weight: 700;
line-height: 1.1;
text-wrap: balance;
margin: 0 0 1.5rem 0;
letter-spacing: -0.02em;
}
h2 {
color: var(--accent);
font-size: clamp(1.25rem, 1rem + 1.5vw, 1.75rem);
font-weight: 600;
line-height: 1.2;
text-wrap: balance;
margin: 2rem 0 1rem 0;
letter-spacing: -0.01em;
}
h2:first-child {
margin-top: 0;
}
p {
text-wrap: pretty;
margin: 1rem 0;
}
a {
color: var(--accent);
text-underline-offset: 0.2em;
text-decoration-thickness: 2px;
text-decoration-skip-ink: auto;
font-weight: 500;
}
a:hover, a:active {
text-decoration-thickness: 3px;
}
button {
padding: 0.75rem 1.5rem;
font-size: 1rem;
font-weight: 500;
font-family: inherit;
color: var(--background);
background: var(--accent);
border: 2px solid var(--accent);
border-radius: 0.25rem;
cursor: pointer;
}
button:hover {
opacity: 0.9;
}
button:active {
transform: scale(0.98);
}
ul, ol {
margin: 1rem 0;
padding-left: 2rem;
}
li {
margin: 0.5rem 0;
}
:focus-visible {
outline: 2px solid var(--accent);
outline-offset: 2px;
border-radius: 2px;
}
button:focus-visible, a:focus-visible {
box-shadow: 0 0 0 3px var(--background), 0 0 0 5px var(--accent);
outline: none;
}
.skip-link {
position: absolute;
left: 0;
top: 0;
transform: translateY(-100%);
background: var(--accent);
color: var(--background);
padding: 0.75rem 1.5rem;
z-index: 1000;
border-radius: 0 0 0.25rem 0;
font-weight: 600;
text-decoration: none;
display: inline-block;
}
.skip-link:focus {
transform: none;
outline: 3px solid var(--text);
outline-offset: -3px;
}
header {
padding-block: 1.5rem 0;
}
main {
padding: 1rem 0;
}
main:focus {
outline: none;
}
section {
margin: 2rem 0;
}
.card {
border: 1px solid var(--border);
border-radius: 0.5rem;
padding: 1.5rem;
background: var(--background);
margin: 1.5rem 0;
}
.card h3 {
margin-top: 0;
color: var(--accent);
}
footer {
padding-block: 1.5rem;
margin-top: 3rem;
border-top: 1px solid var(--border);
font-size: 0.875rem;
color: var(--text-secondary);
text-align: center;
}
footer p {
margin: 0.5rem 0;
}
@media print {
:root {
color-scheme: light;
--text: #000;
--text-secondary: #333;
--background: #fff;
--accent: #000;
--border: #999;
}
.skip-link,
button {
display: none;
}
body {
display: block;
min-height: 0;
max-width: none;
padding: 0;
}
a {
color: inherit;
text-decoration: underline;
}
a[href^="http"]::after {
content: " (" attr(href) ")";
font-size: 0.85em;
font-weight: normal;
}
.card {
border: none;
page-break-inside: avoid;
}
}
</style>
</head>
<body>
<a class="skip-link" href="#main">Skip to content</a>
<header>
<h1>Welcome</h1>
</header>
<main id="main" tabindex="-1">
<section>
<p>This is a well-structured, accessible HTML5 document demonstrating modern best practices for semantic markup and inclusive design.</p>
<p>
It uses semantic landmarks, a skip link for keyboard navigation,
and CSS that adapts to your light or dark mode preference.
</p>
<p>
Text and link colors meet WCAG AA contrast in both themes, type scales
with your browser's font size, and motion respects your system settings.
</p>
</section>
<section aria-labelledby="features">
<h2 id="features">Features</h2>
<ul>
<li>Semantic HTML structure with proper landmarks</li>
<li>Keyboard accessible navigation and focus management</li>
<li>Dark mode support with custom color schemes</li>
<li>Responsive typography using modern CSS</li>
<li>Print-friendly styles for better readability</li>
<li>WCAG AA contrast compliance in all color modes</li>
</ul>
</section>
<section aria-labelledby="examples">
<h2 id="examples">Examples</h2>
<article class="card">
<h3>Component Cards</h3>
<p>Card components are useful for organizing related content. They include a subtle border and padding for visual separation.</p>
<button type="button">Learn More</button>
</article>
<article class="card">
<h3>Interactive Elements</h3>
<p>Buttons and links are fully accessible with clear focus states. The button above demonstrates smooth transitions and proper visual feedback.</p>
<p>Try using the Tab key to navigate through all interactive elements.</p>
</article>
</section>
<section aria-labelledby="resources">
<h2 id="resources">Resources</h2>
<p>Want to learn more about web accessibility and semantic HTML? Check out these resources:</p>
<ul>
<li><a href="https://www.w3.org/WAI/WCAG21/quickref/">WCAG 2.1 Quick Reference</a></li>
<li><a href="https://html.spec.whatwg.org/">HTML Living Standard</a></li>
<li><a href="https://www.a11y-101.com/">A11y 101</a></li>
</ul>
</section>
</main>
<footer>
<p><small>© <time datetime="2026">2026</time>. All rights reserved.</small></p>
</footer>
</body>
</html>
what changed from step 020
+18 / -9 lines
} button {- transition: all 0.15s ease;+ transition: opacity 0.15s ease, transform 0.15s ease; } }⋯ line 210 } @media print {- .skip-link {+ :root {+ color-scheme: light;+ --text: #000;+ --text-secondary: #333;+ --background: #fff;+ --accent: #000;+ --border: #999;+ }+ .skip-link,+ button { display: none; }⋯ line 262 </section> - <section>- <h2>Features</h2>+ <section aria-labelledby="features">+ <h2 id="features">Features</h2> <ul> <li>Semantic HTML structure with proper landmarks</li>⋯ line 274 </section> - <section>- <h2>Examples</h2>+ <section aria-labelledby="examples">+ <h2 id="examples">Examples</h2> <article class="card"> <h3>Component Cards</h3> <p>Card components are useful for organizing related content. They include a subtle border and padding for visual separation.</p>- <button>Learn More</button>+ <button type="button">Learn More</button> </article> ⋯ line 289 </section> - <section>- <h2>Resources</h2>+ <section aria-labelledby="resources">+ <h2 id="resources">Resources</h2> <p>Want to learn more about web accessibility and semantic HTML? Check out these resources:</p> <ul>
What the model said
I made a handful of improvements to `0.html`, but the most important problem is not fixed: the page's CSP style hash is invalid, so browsers will block the entire stylesheet and render the page unstyled.
## Needs your action: the CSP hash
The `style-src` hash on line 5 is 43 characters long; a base64 SHA-256 is always 44, so it cannot match any stylesheet. This was already broken before my edits. I couldn't regenerate it because running the hash command was blocked in this session (no approval available), and nothing has been tested in a browser.
To fix it, run this in the directory and paste the output in place of the existing `sha256-...` value:
```sh
python3 -c "import re,hashlib,base64;s=open('0.html',encoding='utf-8').read();print('sha256-'+base64.b64encode(hashlib.sha256(re.search(r'<style>(.*?)</style>',s,re.S).group(1).encode()).digest()).decode())"
```
The hash covers the exact bytes between `<style>` and `</style>`, so it has to be regenerated after any CSS edit, including whitespace. Chrome's console also prints the expected hash in its CSP violation message.
## What I changed
- **Print colours:** print styles now force a light palette, so printing from dark mode no longer puts light grey text on white paper. The button is also hidden in print.
- **Button transition:** `transition: all` is replaced with `opacity` and `transform` only, the two properties that actually change.
- **Button type:** the button now has `type="button"`, so it won't submit if it ever ends up inside a form.
- **Section labels:** the Features, Examples and Resources sections now have `aria-labelledby` pointing at their headings, so they are exposed as named regions to screen readers.
## Left alone
- **Placeholder URLs:** the canonical, `og:url` and `og:image` values still point to `example.com`; replace them with the real ones before publishing.
- **Author email:** `meta name="author"` holds your email address on a page marked `index, follow`, which makes it harvestable by scrapers. Consider using a name instead.
- **"Learn More" button:** it does nothing, and the CSP blocks all scripts. If it is meant to go somewhere, it should be a link.