Reviews of Free Online HTML Code Validators
Code Error Checkers and Link Checkers

Why you should check your code with a HTML Validator?

The reason you should check your code with a HTML validator it because it can cause some browsers to crash or not display your HTML code properly and most importantly search engine spiders cannot pick up the text off your page with some broken HTML codes. The same goes for broken links on your website as some directories will not accept your submission if you site has broken links. Most search engine quidelines recommend that the HTML code validates also.

To complicate the problem most WYSIWYG programs (What You See Is What You Get) produce HTML code that doesn't validate (FrontPage and Dreamweaver being good examples--even the newest versions are not code compliant with the W3C which regulates HTML code).

Reviews of HTML Code Validators and Error Checkers

The following reviews cover sites offering a free HTML Code Validator, or broken link checker and error checkers. Not all of them provide the same service and some are more thorough than others. If a site is having severe problems I prefer to use the W3C validator first and then the Elsop LinkScan as an HTML validator (it catches broken tags that W3C misses) and a broken link checker and then use the others. The ZDnet validator is good for analyzing download problems. Sometimes if you can't figure out the problem via one HTML validator it helps to check another.

W3C HTML Validator

The W3C HTML Validator Service checks HTML documents for conformance to W3C HTML and XHTML recommendations and other HTML standards. This one is not as user friendly as the others however it is the one more experienced web designers should use. You should have a doc type declaration included and also character type in the meta tags before it will analyze the HTML code correctly. A good explanation of which doc type you should be using can be found at Doc Types Explained. The W3C HTML validator gives an explanation for each error it finds but then you have to understand HTML lingo to figure out what it all means. This analyzer will pick out every single Javascript error in counters, web rings, drop down menus, rollovers, etc. The W3C HTML code validator does not pick up all HTML errors if using the transitional doctype however so use other validators with it, such as the Elsop Link Scan mentioned below because it doesn't always pick up a missing html tag or extra or missing carets, etc.

Elsop Link Scan HTML Validator and Link Checker

The Elsop LinkScan / QuickCheck has a trial version of their HTML validator that checks html code as well as up to 200 links on one page. It has a limit of 10 times per hour. It also provides links to explanations of the errors. It produces multiples of errors on Javascript code however because it is not a Javascript validator so you need to get your Javascript validated elsewhere.

ZDnet HTML Validator and Link Checker

ZDnet validator This HTML validator will let you know if the first 25 links on your site are working (more if you subscribe to their service). It will also spot bad HTML code, check browser compatibility and show you which code is causing the problem on which browser as well as determine download time and let you know how large your page is in code vs images.

Dr. Watson HTML Validator

Dr. Watson also gives you several options for code analysis. Their search engine compatibility test checks your meta tags for the best use of keywords. Dr. Watson provides links to the HTML errors in your code which is very nice.

Javascript Erors in HTML Validators

Many times when using counter codes or codes for web rings or special effects like falling snow on a web page the code may not validate in a HTML validators (even though it is correct Javascript code) because the JavaScript code needs to be upgraded. A good source for JavaScript code that is compatible with all browsers is Dynamic Drive.

CSS Bugs in Modern Browsers

Here is a great site explaining workarounds and demo examples for CSS bugs:
Position is Everything

Reviews of Free Online HTML Code Validators Code Error Checkers and Link Checkers