||Windows, MAC, Linux, UnIx
||Fixes HTML mistakes automatically and tidies up sloppy editing into nicely layed out markup
||HTML Unit Testing tool is a set of classes to make it easy (or at least easier) to automate functional testing. It allows users to specify their tests using a high-level API. This tool should be usable by any QA person with some programming skills.
||HtmlUnit is a java unit testing framework for testing web based applications. It is similar in concept to httpunit but is very different in implementation. Which one is better for you depends on how you like to write your tests.
||Linux, Mac Solaris, Windows
||It is a Web page analysis tool which retrieves an HTML page and reports on any problems that it finds. The primary focus of this tool is to provide a clear, easy-to-use report of information that is relevant for improving your Web page
|W3C HTML Validator
||This is the W3C Markup Validation Service, a free service that checks Web documents in formats like HTML and XHTML for conformance to W3C Recommendations and other standards.