Hi, we are facing more and more issues with the rapidly changing versions of Firefox. Since the release of version 4 there has been new versions released allmost monthly which makes it very difficult to develop websites with a consistant layout across FF versions. I've tried installing standalone portable versions but it seems the FF engine always reverts to the primary engine installed on the machine. I refused upgrading to 7.0.1 and am still using 6 vor development. The problem now is that I cannot test how the site looks in FF 7.0.1 unless I upgrade, which as a Web Developer can have several drawbacks as I then can't see how they are rendered in the previous versions. Now the real issue is that I know for sure that there are layout issues in 7.0.1 that I cannot reproduce in IE6/7/8/9 or Chrome or FF6. This is annoying as I can't develop in the dark and I can't allways run to my boss asking to check if 1px has been adjusted right. Is there anything out there like IETester? I've been searching an I just can't find anything like it for FF. From the marketing perspective I can understand your goal with the major versioning but for us developers it's a pain in the ***. Or am I overlooking something and FF Developertools have an option like IE where you can emulate previous FF versions? This is a major issue and I am really lost right now. The only other option I see is hacking FF installations or installing several operating systems & several FF versions on a machine that is dedicated just for that. Thanks in advance. Greetings, David.