Valid Markup

You're undoubtedly familiar with those little badges that say "This site looks best with browser X". What they unintentionally do is advertise a problem with the site. Turn the phrase around in your mind; it's equivalent to "This site might break on browsers beside X". It's likely that the site looks good with browser X not because X is a better browser, but because the site uses browser-specific markup. By making the site browser-specific, the site has become less usable and more fragile.

Therefore, write markup that validates according to published standards.

Browser-specific markup:

• may break on other browsers
• may break on newer versions of the browser they were written for
• reduces your audience

Writing pages with valid markup:

• ensures that your site is Open To All
• increases the chance that your site will work on future browsers
• lets you focus on creating content instead of resolving browser incompatibility problems

To write valid markup:

1. choose a standard or set of standards (see Appropriate Format)
2. learn the specifics of those standards (HTML, XHTML, CSS, etc)
3. test your pages against those standards

Coping with browsers that don't fully implement standards is a problem. If a noncompliant browser is an important target, you have two options: (1) restrict your site to a universally supported subset of the standards, or (2) use a simpler technology that the browser implements. In other words, choose an Appropriate Format, weighing the importance of the browser in the choice.

Remember: browsers change faster than standards. Use that fact.

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