This isn't a real problem, I think. It's only a minor inconvenience. Every time I spend some time on Firefox (version 2.0.0.3), a small title bar without a window pops up on the lower-left of my screen:

The title bar cannot be right-clicked, can be moved, and closes whenever I press CTRL. So, as you gather, I can't see from the Task Manager which program it belongs to.

What is it, and how do I stop it from appearing? I've tried browsing several websites, and I think it comes up when I visit J2O or JCF, but I'm not sure.

Form1 would refer to a window created hastily inside Visual Basic. I can't say for sure, but I doubt it is related to Firefox, unless as a malware or faulty plugin.

Sounds like VB indeed with some faulty or non-working code that is supposed to hide the window. Can you identify what process it is? There are many programs that allow you to do so. Personally I use Spy&Capture and EnumerationX.

If it appears in the Applications tab of task manager, right-click on the entry there and pick "Go to process" to find out which process is responsible.

Wow, it has no X button.

I've got it! It's my Calvin and Hobbes screensaver. It's quite old and, I imagine, very badly coded (I downloaded it somewhere). It pops up after 3 mins of inactivity, which is the time I set my screensaver at. Instead of the actual screensaver, there is Form1.

And since the moment you go to Jazz2Online or the JCF you're bored to death by us and idle, you usually get it for those sites!