Why it is necessary to validate css and xhtml of a theme...Even with out v
It's not necessary, but it helps with accessability for it to be valid xhtml and css.
It also ensures that it is viewed nearly the same with all the browsers ;)
Well my theme is working fine with both ie and firefox without being validated. But any way i think its good to get valid stuff around thanks for ur time
It can also help search engine crawlers index your site.
Hum now thats a good point :)
why validate? So nobody comes to you and say "you should get that validated"
99% of the time, it makes no difference. But it's good to do it anyway, it's more professional.
Standards are not meant just for "professionalism". Like Chris and Forsakenlad said, it helps with accessibility with every browsers and technologies.
Your page is well displayed in Internet Explorer and Firefox: great, those two browsers are the most used. But what about other browsers users (Safari, Opera, IE Mac, Konqueror, Omniweb, Lynx, ...) or other technologies users (screen-to-voice, cell phones, search engine bots, ...) ?
Of course, you can't test your pages with all theses technologies, so that's why web standards exist: to ensures that your pages are viewed nearly the same with all the browsers.
You seem to be using a wireless browser - that's another reason!
-[Unknown]