Tables are meant to be used for one thing and one thing only and that is the display of tabular data. Please, do not use tables for layout. It is much better left to CSS. Using tables for layout is a messy hack often used to “get pages to look the same [...]

You start your sentences with a capital letter; start your HTML with a DOCTYPE. It’s just basic grammar. - Mark Pilgrim from Dive Into Accessibility
Using a complete doctype will switch your browser into standards mode. This will cause it to render the page exactly as you have instructed it (which may look awful but [...]

Developing a website without validating is like running around with a blindfold on. As soon as you ask for directions, don’t be surprised if the only answer you’ll get is “take your blindfold off”. - some guy named Jim
Validate your markup here
Validate your CSS here

Firefox is a standards aware browser. The authors are actively involved in squashing bugs and making it work the way it should. When FF is switched to standards mode with a proper doctype everything works as expected.

IE is the bane of every serious web designer. Some things you are going to want to look up are

peekaboo bug
line-height bug
guillotine bug
duplicate character bug
italics bug
double float margin bug
three pixel jog
escaping floats bug
creeping text bug

These are addressed at Position is Everything

The steps before this one are necessary. Good clean code is hard enough to debug. Code with bunk markup and presentational hacks just throws more hay on top of your needle. Taking the steps above before asking for help shows that you are at least trying. To drive that point home [...]