I know you can put conditional statements to load different CSS files if you are in Internet Explorer, but can you do this inside of a CSS file?
I have a situation where I want the right margin to be 20 if it's Internet Explorer but 10 if it's any other browser.
The easiest way to handle this is with conditions in your HTML that put a div with a specific id around the rest of the page.
<!--[If IE 8]>
<div id="IE8">
<![endif]-->
.
.
.
<!--[If IE 8]>
</div>
<![endif]-->
Then, your CSS can do this:
#IE8 div.whatever { ... }
This sort of makes all those CSS hacks unnecessary.