How to deactivate the pop-up blocker in Mozilla
Mozilla is an Open-Source Web Browser, which has been written mainly for use by web designers.
The browser has an integrated pop-up blocker. That means that you are protected from annoying pop-up adverts but, on the other hand, you do not receive welcome pop-ups such as quickmessages, menus oder media pop-ups.
How to deactivate the pop-up blocker in Mozilla

Click on "Edit" (Bearbeiten) and open the "Settings" (Einstellungen) menu.

Click on "Advanced" (Erweitert) and then on "Scripts & Plugins" (With Mozilla 1.0 Scripts & Windows). Make sure that under "Allow following actions on websites" (Webseiten folgende Aktionen erlauben), the option "Open non-requested pages" (nicht aufgeforderte Seiten öffnen) is activated. Confirm the changes by clicking on "OK".