If you are a web professional then you need to test your creation in majority of web browser. I am running Firefox and IE7 on my PC. I just created a three column design using CSS that is working fine in Firefox and IE7 on my PC. Then, i just checked design on another machine having IE6 version. The appearance was totally different in IE6 and was very ugly. but the same code was working well in Firefox and IE7.. I just search google to fix the issue.. finally come up with the solution that i need to create new CSS file for IE6. I need to detect browser version in program and use different file depend on the IE version of the browser. You also need to have both version of IE to test compatibility in both version. However, installing IE6 and IE7 on the same machine is little tricky.. If you have installed IE6 and want to use IE7 along with IE6 then try Jon Galloway IE7 stand alone version. If you have IE7 installed then try no hassles IE6 stand alone version. No installation required. Just unzip zip file and run iexplore.exe file to run IE6 independently.