One of the things I've started doing recently when creating new templates is adding the wildcard tag and giving it a padding and margin of 0.
Code:
* {
margin:0;
padding:0;
}
Both IE and Firefox (and Safari and Opera etc etc etc) handle their inherent paddings and margins differently. For instance, the LI tag might have a padding of 4 in IE and a padding of 2 in Firefox. Adding the wildcard kinda sets everything to a default and then you can go to each element and give it padding/margins to your desire.
Thats just my way around the 'works in IE not in firefox or vice-versa' issues. I'm sure there are many others
