Delorie Software provides a number of free services to the web community to assist web authors who wish to make their information available to the largest audience. These tools provide alternate ways of viewing your pages, so that you can ensure that your content is received properly by all viewers. This is an incredible free service that all webmaster's should use "at least once!"
NetMechanic provides and incredible "7" free html services all in one spot. HTML validation, gif reduction, server check, and many more. This is a great place to check your site for html standards and correct any errors you find. Give it a try, you'll love it!
This is one intense service folks. It checks your page for tons of different errors and lists them by line. It also posts possible remedies for your errors. This is a very thorough service and will take a bit of time to finish but is well worth the wait. You should be somewhat familiar with html syntax to use this service. Highly recommended.
Bobby is a web-based public service offered by CAST that analyzes web pages for their accessibility to people with disabilities, as well as their compatibility with various browsers. The analysis of accessibility is based on the working draft of the W3C's WAI Page Author guidelines, with the Page Authoring Working Group's latest revisions. All pages on your web site must meet these requirements to display the Bobby Approved icon.