HTML differences between browsers

Question

Do you know of any differences in handling HTML tags/properties in different browsers? For example, I once saw a page with a input tag with a maxlength field set to "2o". Firefox and Opera ignore the "o", and set the max length to 2, while Internet Explorer ignores the field altogether. Do you know of any more?

(Note: seeing as this will probably be a list, it would be great if the general name of the difference was in bold text, like: Different erratic value handling in tag properties)

Answer 1

Bug Lists

Web developers have already compiled some pretty comprehensive lists; I think it's better to compile a list of resources than to duplicate those lists.

• http://www.positioniseverything.net/
• http://www.richinstyle.com/bugs/table.html
• http://www.quirksmode.org/ (as mentioned by Kristopher Johnson)

Javascript

I agree with Craig - it's best to program Javascript using a library that handles differences between browsers (as well as simplify things like namespacing, AJAX event handling, and context). Here's the jump to Craig's answer (on this page).

CSS Resets

CSS Resets can really simplify web development. They override settings which vary slightly between browsers to give you a more common starting point. I like Yahoo's YUI Reset CSS.