This is a quick trick I picked up to guarantee that any css changes you make only affect what you want. There are different ways to identify the page you need to change. I tend to use url as it's always unique. Here's how:
We've all experienced it, you've themed out a page and it looks fantastic in Firefox. Unfortunately the time has arrived for your IE testing... You've dreaded it the entire time and have put it off. You fire up your windows testing environment and your worst nightmare has come true. The entire layout is blown out. Divs are strewn about like your tpl.php ate a hand grenade.