My website works in IE but jumps in mozilla firefox

[butifaro]

Hi there all
I have used dreamweaver to design a website

http://www.abbey-centre.com.

I dont understand html so I dont
really know what is going on with the coding.

the site looks fine & works on my pc in Internet explorer but when I look at it with Mozilla Firefox it jumps all over the place when loading and the rollover image navigation buttons dont swap images.

I really have no idea what is going on

please can someone help

Any other comments on how to improve the site would be much appreciated too.

thanks
janine