HTML 3.2 Validator
This validator is not very strict, but will give
you a good idea if your HTML is pretty sound. You might see a
few minor errors.
Really
Fussy 4.0 HTML Validator
W3C HTML Validation Service
Easy-to-use
HTML validation service based on an SGML parser. It checks HTML
documents for compliance with W3C HTML Recommendations and other
HTML standards.
WPMultiSite.com Manage Multiple WordPress Sites From One Installation (easy update)
HTML
Validation
HTML 3.2 is not the current
specification, but many users don't use browsers that support
the latest specification. As a web site designer its well
worth it to you to obtain the latest version of browsers. You
probably have an updated operating system with plenty of tools
to help you deal with downloading and installing software. Many
users not only don't have the latest browser, but don't have the
update tools that make it easy for them to upgrade to the latest
software. That's why its important to keep your site compatible
with the older specifications.