So this was a stupid mistake. After I moved the tester to the "/tester" subdirectory, I removed some of the unnecessary CSS that no longer needed to be applied to the page. I didn't even think to check the site in all of the different browsers again because I hadn't done much. Apparently though I had forgotten something very important... #silverlightControlHost { height: 100%; } I needed to add that little bit of CSS back into the page. Without it Regex Hero was completely invisible to Firefox users. I am sorry about this problem. I wasn't told by anyone that there even was a problem. And I overlooked it because I rarely use Firefox. Anyway, it's solved now. This brings something else to my attention. I'd like to be contacted if there are any problems. But perhaps the GetSatisfaction thing is too much of a hurdle for some people. So I think I'll add a Contact page to the site. That way you can email me directly or use GetSatisfact
Dedicated to the online C# regex tester at regexhero.net