Also know that browsers render pages differently, all depending on how they handle invalid HTML, what tags they support, built-in fonts, etc. This ofcourse also is the case for different browser versions. IE3.0 will render differently than IE4.0. IIRC websitegarage provides a similar service.

Update: broken link fixed, kudos to blakem

Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.