web page validation question? [ROUND 2]

Question

when using JQuery, HTML is it mandatory to make your web pages validate even when JQuery, can sometimes mess up your html for instance when using the slideDown on multiple links on the same page.

Answer 1

jQuery shouldn't ever be "messing up" your HTML. (What exactly do you see it doing that's producing invalid markup?)

Having said that, the same requirements for validation apply after using jQuery as apply before using it. Some browsers may respond fine to certain validation errors, while other browsers may render the page incorrectly. Having valid markup is almost always preferable to having invalid markup.