It was last released 10 September 1997 as version 1.020. WebLint 2 is in the works, though, with the last release April 1999.
You can also try the much more current, w3 approved versions (HTML Validator and CSS Validator)
[Personally, I call the w3 services "web lint and CSS lint" in homage to the original. -- SunirShah]
WebLint parses your web pages and tells you when you deviate from the standard. In general, sticking to the standards is a good way to a) be portable, b) be accessible, c) be LynxFriendly. Also, it gives you the right to blow off Netscape users who complain that your page is ugly or hard to read. Netscape isn't standards compliant.
It is very difficult to make snazzy pages lint clean, or lint clean pages snazzy, but it's possible. Provide, of course, you don't care about Netscape. BadBrowsersMustDie.