CSE 3310 HTML Validator.  A very nice Windows based HTML validator.  This validator can integrate with several popular HTML editors.

Netmechanic.  Netmechanic offers two free robot services.  The first service is a link checker.  The second service is a HTML validator.  Either of these services can be run while you wait, or run as robots and then e-mail you the results when they finish.

Link Scan.  Link Scan is a powerful server based perl script for validating your sites links.  Link Scan can check both internal and external links.  Link Scan can validate multiple external links at one time, which greatly speeds up the process.  Our site uses Link Scan to validate our links.  This is a commercial product with a 14 day evaluation.

Bobby.  Bobby is a different kind of HTML validator.  Bobby checks that your HTML is valid for numerous popular browsers as well as checking that your page is accessible for people with disabilities.  Bobby was created by CAST (Center for Applied Special Technology).

W3C HTML Validation Service.  This validation service validates one page at a time.  It strictly checks HTML syntax.

Dr. HTML.  This validation service can validate one page or a whole site.  Dr. HTML does not strictly check HTML.  Nice features include spell checking and suggested image size.

weblint is a perl program that syntax checks your HTML.  It must be uploaded and run on your web server.

MOMspider is a perl program that verifies all the links within and out of your web site.

Webxref is a perl program that verifies all the links within and out of your website.