This is actually a change made by Apple is Mac OS X Lion. You can change the Scroll Bar settings by going your Mac's System Preferences, General, and under "Show scroll bars:" change it "always". Let me know if this helps.

Thank you very much for your answer, but that's not it.

I'm using OS 10.5.8. There is no General heading under preferences, and I looked under any settings that could have a scroll bar preference, and didn't find an option to keep scroll bars on.

There is nothing in Firefox preferences that governs the appearance of scroll bars either. So I remain convinced that it's a setting built into Firefox.

If your running Mac OS X then by default scroll bars are disabled in the operating system settings. Perhaps someone with more Mac knowledge can fill you in on this.

Thanks for answering, weather 15. I found the info on the Lion OS, and I see what Apple is doing. Still doesn't explain why I don't get the scrollbar in my older OS. Anyway, I guess I'll have to adapt and just use my up and down arrows and page up and down on the keyboard, that's probably better anyway. I'm using an old mouse because my nice iMac mouse had its tail pulled out.