firefox displays different in vista than xp (why?)

[Captainkewl]

Does anyone know why firefox displays this webpage differently in vista than it does in xp. It is the same version of firefox, one running on vista and one on xp.
I attached screenshots.

Kris

[Harry]

Because you've not coded it very well.

http://validator.w3.org/check?verbos...2Fcontact.html

[Scriptage]

It still has the same rendering engine though, it may be something to do with the preferences in the browsers (<-- stab in the dark).