"jumping" screen when using Firefox

Whenever I'm in Yahoo Mail, my screen jumps 1 line–alternating up, then down–every 5-15 seconds. While composing e-mail, when I get ready to click on something or type something, the screen will jump and cause me to click on something I don't want, or type something in the wrong place. It's also extremely annoying to try to read mail. This does NOT happen anywhere except in Yahoo Mail, and it does NOT happen when I use IE–it happens ONLY when I use Firefox. Thanks for any suggestions.

You will get better answers in the FireFox forum I think.

sounds to me like some type of auto refresh that is causing that page to keep jumping to the top, sorry i don't have a quick fix.