In this day and age, I try to avoid image replacement as much as possible but when necessary i tend to use the old -9999px technique. This is an interesting alternative without so many drawbacks.

Tiny (1KB) javascript tool that allows you to easily target specific browsers with CSS by adding a class to the html tag!

great tutorial detailing how to use CSS hacks to target any of the major browsers.

Having trouble with CSS Min-height and min-width in older browsers? This CSS hack from Dustin Diaz will fix that right up for ya!