HTML formatting

Follow Google's HTML/CSS Style Guide. Exception: don't leave out optional elements.

In particular, following are some basic guidelines from that style guide, which generally apply to other documentation source files, too (such as YAML and Markdown):

  • Don't use tabs to indent text; use spaces only. Different text editors interpret tabs differently, and some Markdown features expect spaces and not tabs.
  • Indent by two spaces per indentation level.
  • Use all-lowercase for elements and attributes.
  • Don't leave trailing spaces at the end of a line (except as needed for Markdown).

Line length

Break lines at 80 characters except in the following cases:

  • Information in a meta element at the beginning of a file must be on a single line, so those lines can be as long as needed.
  • If a URL in a link has a line break, the link won't work. If a URL is longer than 80 characters (quite common), you're stuck with it. In that case, put the URL on its own line with the href attribute to make it easier to review the text before and after, as the following example shows:
  • You can find more information in
    <a href="…-von-hautkopf-of-ulm.html"
    >his biography.</a>

Break code snippets (in <pre> blocks) at 80 characters:

  • Older files might use different line lengths. If you're making small changes to a file that has a consistent line length other than 80 characters, then make your changes conform to that file's line length rather than reformatting the whole file.
  • When adding line breaks, make sure that you don't change the meaning of the code! If you're not familiar with the programming language, ask for help from someone who is. But sometimes you just can't avoid a long line.