Total Validator Tool
Use just one tool to check (X)HTML, accessibility, spelling and broken links.
The Total Validator Tool performs the most important validations on your web pages: True (X)HTML validation against published W3C/ISO DTDs; accessibility validation against the W3C and US Section 508 guidelines; spell checking against one of five languages; and testing for broken links.
Spelling is often left unchecked and will make your site look and feel unprofessional and even unusable. Broken links are the bane of every webmaster, you may get your internal links correct, but external sites tend to change all the time, and there's nothing that makes your site look worse than a link to nowhere. So you need to regularly check your site for broken links. If you need more than the this tool provides then keep a look out for the full version that allows you to test more than a page at a time, has many more options and CSS Validation.