I think having valid HTML and CSS does wonders for your site, it makes it easier to be read by search engines too, however i've no idea how much it'll affect your SEO, though i'd recommend making things as coherent as possible, as it's not worth the risk, and sloppy coding is never good either in most eyes. Though the CSS will only change the aesthetics, the HTML will take the bulk of the SEO related properties. If you're going to do a job, do it properly, ensuring you remember things like as the ALT property in images etc, and using the H1 tags... the list could go on...
If I recall correctly, one time Matt Cutts said that W3C can't be used as ranking factor, because many many big sites don't care about it.
Yeh, well im terrible with SEO and i didn't design the site so i never had realised before. Ill head over to w3schools learn some css and fix it now! Thanks
It doesn't make any impact on your website directly...However, you should validate your website so that SE crawlers can find their way in the website..
yeah, better for the crawlers. I would have said some boost in SEO, but if Cutts said no, possibly for Yahoo and others though.
evenif W3C doesn't count much for google , it is good to make it validate , since you may get benefit from other SE
IT can matter somehow actually, it will lesser your code and then it helps in quick indexing of the page.
the w3c validation is not related to SEO in any way but people recommend to get the site w3c validated. the reason is that robots come to website for very small time. if your website is w3c validated, then robots will find it easy to crawl and rate too will be fast. therefore, more and more of your website will be crawled as your site will be following the W3C terms.