If it's mostly IE you're having problems with, have a look at IE's 'conditional comments'. You can specify code you only want to be visible to IE, or specific versions of IE. This means you can write your CSS for the more standards compliant browsers, and include IE hacks in one file like so:
<head> <!--[if IE]> <link rel="stylesheet" type="text/css" href="ie-hacks.css" /> <![endif]--> </head>
See CSS - Conditional comments
Joel.
