Mozilla Firefox's pop-up blocker is on by default. To change the Firefox's pop-up blocker settings you will need to follow the steps below:

1.) Click on the icon pictured below (it is in the upper right hand corner of the screen) and then click Options button at the bottom of the menu that appears.

2.) In the menu that appears click on the "Content" tab.

3.) If you would like to allow all pop-ups from all websites (NOT recommended) you can change that option here by unchecking the "Block pop-up windows" option. If you instead would like to allow a single website to display pop-ups, click on the "Exceptions" button.

4.) In this menu you can allow certain websites to display pop-ups. Simply copy and paste the URL of the website into the box labeled "Address of website" and then click the "Allow" button.