One tool I’m using to help with cross browsers issues is Modernizr. It’s a piece of JavaScript that uses feature detection to give you booleans to refer to in terms of what the user’s browser supports, and more importantly, what it doesn’t. So for example, right now I’m using the following snippet to handle rounded corners (border-radius) in browsers that don’t support them.

if(!Modernizr.borderradius) {
  // Do stuff to handle browsers without border-radius support
}

What’s great about it is that it doesn’t use browser sniffing for feature detection. It’s not just a list of browser versions and their corresponding features, it actually attempts to use the features’ namespace, and sets a boolean if the attempt succeeds or not. Very cool.