victor - 8:16 am on Jun 15, 2003 (gmt 0)

A!DOCTYPE tells a browser unambiguously what variant of HTML or XHTML you are using.

Without it, each browser may interpret some tags differently, leading to a rendering that is more varied between browsers than you'd want.

Without it, many browsers will drop into "quirks" mode -- meaning they'll assume you've coded to match their bugs. If you've actually written clean, validated code chances are this means they've mis-interpreted some of your code.

With it, you aren't guaranteed that browsers won't exhibit bugs -- after all, they all have them, but you are better assured that the page will render correctly across a wide range of browsers.

Some more information at:

[oreillynet.com...]