Alert Preferences
To view these options right-click on the system icon and select "Display Pop-up Preferences"

The Alert Preferences window is developed so that you can visually see which sites you have blocked and which sites are allowed to have pop-ups.  This feature can be toggled from the main screen. (See: Main Screen)

The sites listed in Green are the sites that you have granted access to allow pop-ups
The sites listed in Red are the sites in which you have blacklisted from displaying pop-ups

-You can remove a URL from the list by clicking on it then pressing the "remove" button
-You can toggle the pop-up preference by clicking on the URL and then selection "Always Allow" or "Always Block".