W3C Markup Validation

W3C provides a free web site validator available here that allows you to determine if your site is made up of completely valid XHTML. After running a few major sites through the validator, it appears that many of the popular sites do not actually validate as correct code. It seems that as long as a site looks good in most browsers (hopefully), the content creators don't seem to care very much whether or not the code is correct (standards-compliant). Hopefully in the future, more sites will make use of the validation service in order to ensure correct rendering in all standards-compliant web browsers.