CSS Differences in Browsers

My websites shows a button differently in different browsers. How the button works is that you hover over it, the top one disappears using “hover” in the css and it shows the button below which all works fine.

On the top button there are two parts – a price and a description both in their own divs and/or spans. These parts are interpreted differently in browsers. I have been basing my CSS for the website to work in Firefox, but they look differently in all other browsers. I think it might be something to do with the “margin”, “left”, “right” and “position” attributes in the CSS. The “position” for each of them is “absolute”.

So can someone tell me why this is, and what to do about it?

A quick answer would be great thanks.