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Style Guide for HTML

General

  1. 4-space indentation
  2. Use slashes in self-closing elements (eg <img />, <hr />), including <meta>

URIs

In accordance with RFC3986, Section 3:

foo://example.com:8042/over/there?name=ferret#nose

// vs https://

Protocol-relative URLs (//) are now considered an antipattern. Use https:// and http:// instead.

Link Text

In accordance with HTML Techniques for Web Content Accessibility Guidelines 1.0, Section 6.1.

Do not use click here as link text.

Do not use call-to-action verbs like go to our page.

Use the page or content your are linking to as the text instead.

Bad

[Click here] to visit GitHub.

Also bad

Click here to [visit GitHub].

Good

Click here to visit [GitHub].

Attribute Order

  • class
  • id, name, content
  • rel, data-*, hreflang
  • src, srcset, for, type, charset, sizes, href, media, value
  • step
  • title, alt, placeholder
  • (checked), (selected), (disabled)
  • (required), (autocapitalize), (autofocus)
  • async, defer, integrity, crossorigin
  • aria-*, role
  • style

HTML5 Containers

Use HTML5 containers like

  • <main role="main">
  • <header role="banner">
  • <article role="article">*
  • <section role="region">*
  • <nav role="navigation">
  • <footer role="contentinfo">
  • <aside role="complementary">

* article and region are not ARIA landmarks.

Navigation

Do not use

<ul id="site-navigation" role="navigation">
    <li><a href="#">Home</a></li>
    <li><a href="#">About</a></li>
    <li><a href="#">404</a></li>
</ul>

Instead, use

<nav role="navigation">
    <a href="#">Home</a>
    <a href="#">About</a>
    <a href="#">404</a>
</nav>

Two significant differences between the two:

  1. First, ul#site-navigation is replaced with nav.

  2. Second, the navigation no longer contains list items, only links.

    The argument for this is that a screenreader will read the first case as

    List item 1: Home; List item 2: About; List item 3: 404.

    Which is way too belaboured for a user. The latter example is better UX.

You can optionally wrap the links in <span>. You can also give the <nav> element an id.

Footnotes

  • Place footnote link for paragraphs after the fullstop, with a space
    • except if a sentence follows in the same paragraph.
  • Be sure to namespace the footnote IDs, if several footnotes exist on the same page in different contexts, eg different blog posts on a front page.
  • Wrap block footnotes in <aside>.
The bad example implies a 100% certainty betrayed by factors like variance and methodology.<sup id="fn-link-1"><a href="#fn-text-1">1</a></sup>

<!--***-->

<aside role="complementary">
    <ol class="footnotes">
        <li><sup id="fn-text-1"><a href="#fn-link-1">1</a></sup> To gain a better understanding of all the caveats of conducting a poll and interpreting the results, check out the <a href="https://ndarville.com/projects/metapoll">Metapoll</a> project.</li>
    </ol>
</aside>

Images

<a href="https://example.com">
    <picture>
        <source
            type="image/jpeg"
            srcset="image.jpg 1x, image@2x.jpg 2x" />
        <img
            class="image"
            src="image.jpg"
            alt="Alt text"
            title="Title text" />
    </picture>
</a>

Videos

<video controls poster="thumbnail.png" preload="none">
    <source type="video/mp4"
            src="video.mp4" />
    <source type="video/webm"
            src="video.webm" />
    <source type="video/ogg"
            src="video.ogv" />
</video>

You can also use preload="metadata", if the situation calls for it.

Figures

<figure> is an easy way to wrap media, tables or lists contexually, especially for labelling purposes.

<figure aria-labelledby="fig-cap1" role="group">
    <picture>
        <source
            type="image/jpeg"
            srcset="image.jpg 1x, image@2x.jpg 2x" />
        <img
            class="image"
            src="image.jpg"
            alt="Alt text"
            title="Title text" />
    </picture>
    <figcaption id="fig-cap1">Description.</figcaption>
</figure>

Alerts

  • Use the ARIA role="alert" to inform assistive technologies of a time-sensitive and important message that is not interactive. If the message is interactive, use the alertdialogue role instead.

Forms

Always use for in <label> and id in <input>. When sending data to a webserver, include name in your <input>.

  • All form control tags should have an associated label.
  • Any additional information—such as required, optional, or example text—should be wrapped within the label tags. For example: Favorite Pie Optional. This way screen readers know what additional information is related to each field.

Use aria-describedby for error messages.

  • Avoid placeholder text for accessibility reasons. Most browsers’ default rendering of placeholder text does not provide a high enough contrast ratio.
  • Avoid breaking numbers with distinct sections (such as phone numbers, Social Security Numbers, or credit card numbers) into separate input fields. For example, use one input for phone number, not three (one for area code, one for local code, and one for number). Each field needs to be labeled for a screen reader and the labels for fields broken into segments are often not meaningful.

Choose input type based on the size and length of input; in ascending order:

  • Radio
  • Checkbox
  • Dropdown (options)
  • Text input with autocomplete (eg <datalist>)
  • When most users will (or should) pick a particular option, make it the default: <option selected="selected">Default</option>

Checkboxes

Surround a related set of checkboxes with a <fieldset>. The <legend> provides context for the grouping. Do not use fieldset and legend for a single check.

Think of <legend> as <label> for an input group.

Avoid using negative language in labels as they can be counterintuitive.

Templates

  • Display form controls in the same order in HTML as they do on screen. Do not use CSS to rearrange the form controls. Screen readers narrate forms in the order they appear in the HTML.

  • Keep your form blocks in a vertical pattern. It’s an ideal approach for accessibility, due to limited vision that makes it hard to scan from right to left.

  • Leave the title and suffix fields as text boxes instead of offering drop downs. There are many possible titles and suffixes; text boxes accommodate them all.

Scripts

For externally loaded content, always use a checksum hash (integrity for scripts, ie Subresource Integrity Hash) and crossorigin="anonymous". See srihash.org.

async and defer

defer and async only work for <script> tags where src is defined.

The two boolean attributes exist to prevent blocking.

async

  1. Download in the background without blocking
  2. When finished downloading,
    • block and execute
  3. Rendering resumes

defer

  1. Download in the background without blocking
  2. When finished downloading,
    • block and execute according to the order specified in the DOM
  3. Rendering resumes

Unfortunately, browsers use defer differently, which usually makes it run similarly to async.

async defer

async overrides defer, so using <script async defer> is equivalent to async with better browser support.

Further Reading

Example Script

<script
    id="github-bjs"
    type="text/javascript" charset="utf-8"
    src="https://buttons.github.io/buttons.js"
    async defer
    integrity="sha384-egYe2iLG/VUblwMVWC7scltVz2CuhgfU0q4mfHYmtuemlb5VSNAyNCpMxbH5uLxJ" crossorigin="anonymous">
</script>

Further Reading

Typefaces

@font-face CSS

@font-face {
    font-family: "EB Garamond";
    font-style: normal;
    font-weight: 400;
@if $avoid-local-font == true {
    src: local("");
} @else {
    // PostScript font name for Safari `local`,
    // Full font name for rest
    src: local("EB Garamond"),
         local("EBGaramond");
}
    src: url("EB-Garamond-regular.eot"); // IE9 compat mode
    src:
        url("EB-Garamond-regular.eot?") format("embedded-opentype"), // "?" for IE6-IE8
        url("EB-Garamond-regular.ttf") format("truetype"),
        url("EB-Garamond-regular.woff2") format("woff2"),
        url("EB-Garamond-regular.woff") format("woff");
    unicode-range: // Optional for limiting characters
        U+0061-007A, // a-z
        U+0041-005A, // A-Z
        U+002D;      // -

Read more about this and all the many caveats in “Bulletproof @font-face syntax” by Paul Irish.

Performance and Optimization

Defeating FOIT

Change your stylesheet from including the custom font that looks like so:

body { font-family: "Raleway", "HelveticaNeue", "Helvetica Neue", Helvetica, Arial, sans-serif; }

To this:

- body { font-family: Raleway, HelveticaNeue, "Helvetica Neue", Helvetica, Arial, sans-serif; }
+ body { font-family: HelveticaNeue, "Helvetica Neue", Helvetica, Arial, sans-serif; }
+ .fonts-loaded body { font-family: Raleway, HelveticaNeue, "Helvetica Neue", Helvetica, Arial, sans-serif; }

At the bottom of the HTML body, add the following using Font Face Observer:

<script type="text/javascript" src="/static/js/fontfaceobserver.js"></script>
<script type="text/javascript">
    var raleway300 = new FontFaceObserver("Raleway", {"weight": 300}),
        raleway400 = new FontFaceObserver("Raleway", {"weight": 400}),
        raleway600 = new FontFaceObserver("Raleway", {"weight": 600});

    Promise.all([
        raleway300.check(),
        raleway400.check(),
        raleway600.check()
    ]).then(function() {
        document.documentElement.className += "fonts-loaded";
    });
</script>

This defeats FOIT (see below) by loading the fallback fonts first and then applying the custom fonts, once, and only once, they’ve finished downloading.

Deferred Font Loading

External

Either retrieve web fonts from Google Fonts:

<!-- Preconnect to external font -->
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
<!-- Delay download of font until document is loaded -->
<link rel="stylesheet" type="text/css" href="https://fonts.googleapis.com/css?family=Raleway:300,400,600" media="deferred" onload="if(media!='all')media='all'" />
<noscript><link rel="stylesheet" type="text/css" href="https://fonts.googleapis.com/css?family=Raleway:300,400,600" media="all" /></noscript>

Just place the preconnect immediately before the font loading to parallelize the operation; little need to put it in the front.

You can explore using dns-prefetch as well.

Local

Or load them locally using localfont.com. (Another option is webfont-dl, which I personally have not used.)

<!-- Delay download of font until document is loaded -->
<link rel="stylesheet" type="text/css" href="/static/typefaces/css/fonts.css" media="deferred" onload="if(media!='all')media='all'" />
<noscript><link rel="stylesheet" type="text/css" href="/static/typefaces/css/fonts.css" media="all" /></noscript>

What’s with the Media Type?

It defers the downloading (ie blocking) of the fonts, until the page has finished loading. That way, the fonts won’t block the rendering of the page; fonts are often the bottleneck in loading a page.

This solution will result in, brief, FOUT (see below), but between FOIT and FOUT, the latter is preferable, unless the target audience always uses a high-speed Internet connection.

FOUT, FOIT, FOFT

Flash of text that is:

  • unstyled
  • invisible
  • faux

Learn more about at this GitHub issue about the travails of font loading and rendering.

Optimizations and Enhancements

Prefetching and Prerendering

<meta http-equiv="x-dns-prefetch-control" content="on" />

  • prefetch: prefetch resource for future page
  • subresource: higher priority than prefetch for current page
  • prerender: prerender future page in background
  • dns-prefetch: advance DNS lookup for current page

Others

  • preconnect: start connection handshake early
  • preload: forced prefetching

Examples

Place your pre-* tags at the very top, preface them with http-equiv="x-dns-prefetch-control", and group them together based on URIs.

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta http-equiv="x-dns-prefetch-control" content="on" />
        <link rel="dns-prefetch" href="https://fonts.gstatic.com" />
        <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />

Further Reading

  1. Preconnect, prefetch, prerender ...
  2. Prefetching, preloading, prebrowsing

next and prev

Remember to use <link rel="next" /> and <link rel="prev" />, if there is a sequential relation between two of your pages.

<meta>

  • name="description" content="{{ page.description }}"

  • name="author" content="{{ page.author }}"

  • http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"

  • name="viewport" content="width=device-width, initial-scale=1"

Open Graph

  • property="og:title" content="{{ page.title }}"
  • property="og:description" content="{{ page.description }}"
  • property="og:url" content="{{ page.permalink }}"

Optional

  • property="og:type" content="article"
  • If HTTPS: property="og:image:secure_url" content="https://ndarville.com/hotlink-ok/image.png"
  • If HTTP: property="og:image" content="https://ndarville.com/hotlink-ok/image.png"
  • property="og:image:type" content="image/png"
  • property="og:image:width" content="192"
  • property="og:image:height" content="192"

Twitter (Optional)

  • name="twitter:creator" content="@pessimism"
  • name="twitter:site" content="@HafniaTimes"
  • name="twitter:description" content="A Danish publication in English promoting open data and transparency in tech and politics."
  • name="twitter:card" content="summary_large_image"

Language

  • <html lang="en">
  • property="og:locale" content="en"

Alternate Languages

  • <link rel="alternate" hreflang="da" href="/da" />
  • property="og:locale:alternate" content="da"

Language Codes

There are three types of language metadata:

  1. <html lang="">
  2. <link rel="alternate" hreflang=""> /
  3. <meta property="og:locale" content="" /> #
    • (And of course og:locale:alternate)

Unless required by specificity, stick to the ISO 639-1 language format.