Why is it good to be XHTML and CSS Strict (Valid)

[zulufox]

I have been looking at Mambo 4.5 as a good CMS, however, I see now that their is XMambo 4.5 which has been modified to be XHTML and CSS Valid (I doubled checked that myself).

What are the advantages to being Valid? Do you get more google-bots? Do search engines choose your site more?

Thanks

[Fischerlaender]

There are serveral good reasons in this thread [webmasterworld.com].