This should be set as the default in Firefox, IMHO. But it sure is nice not having exploding browser windows anymore!
There is nothing more annoying than pages that resize your Firefox Window.
Luckily, you can fix it within seconds.
Here is how to prevent sites from resizing your Firefox window:
1. Go to: Tools -> Options -> Content
2. Click Advanced button
3. Uncheck the box “Move or resize existing windows”