In a life where every browser renders the same way you don’t need to worry about cross browser compatibility, but until that time maybe some hints and tips will help you out (and me when I forget and have to search again!)
I’ll be adding to this list as I find more irritating cross-browser compatibilities…
Display your site the same across all Browsers
First and foremost…
Always have at least two browsers open while building and testing the site. Do not leave it til you are ‘finished’ to have a look and then try to fix things that are wrong. I usually choose IE6 and FireFox 2.0. This way you will notice problems immediately and be able to easily rectify the differences (usually).
Watch your padding carefully
Padding likes to render differently within individual browsers. Margin is your better friend in most cases and should display more consistantly throughout.
Floats and widths
From my experience, IE6 could care less in most cases if you allocate a width on a floated item but FireFox will demand one to display properly. Make sure that any items with float:right or float:left’s also have some sort of a width associated to them.