HTML checkers

[Commerce Brian]

Here's an old favourite of mine for checking the HTML, to make sure the tags are fine:
 
http://www.doctor-html.com/RxHTML/cgi-bin/single.cgi

[Commerce Brian]

Also, don't forget, of course, the HTML validator here:
 
http://www.htmlhelp.org/tools/validator/direct.html
 
For for W3 compliance, though.

[Gabriel]

The best checker is the naked eye. A lot of the very bad mistakes come through visually on the browser screen. Other errors can be very obvious in the code itself. It is better to make sure you separate your code elements well and easily so you can debug more easily.