What web browser are you using? In Safari go to the Safari menu and select Block pop-up windows, which is presumably checked. Selecting it will un-check it, allowing pop-ups.
If you use FireFox, open the Preferences (in the FireFox menu) and go to the Content tab. Uncheck the box for Block pop-up windows.
If you use another browser you will need to let us know which.
Best of luck.