It's actually quite simple IF you don't mind getting rid of javascript support. I only know how to do this in IE though. . .
1. Go to the tools menu
2. Select "Internet Options"
3. Click on the "Security" Tab
4. Select the icon the the Earth that says "Internet" under it
5. Click on "Custom Level"
6. Scroll down to where it says "Active Scripting"
7. Click "Disable"
Click ok out of all of the menus and you won't be bothered by popup again, without having to install any special software!