That's something you should manage with Firefox settings; read for instance

http://support.mozilla.org/en-US/kb/Pop-up%20blocker

but also:

https://addons.mozilla.org/en-US/firefox/addon/adblock-plus-pop-up-addon/

Unfortunately, adblock is sometimes interfering with other Google products functionality; in that case, you should disable it....

Hope that helps
Aldo