The Yahoo! Toolbar is available from Yahoo! as part of their service's offerings. The graphic image below is how the bar will appear within Internet Explorer:
The following icon is the Pop-up Blocker: 
To disable pop-up blocking, click on the Down Arrow to bring up the Menu:
Uncheck the entry Enable Pop-up Blocker.
To turn the Pop-up Blocker back on, you can go back in and recheck the entry to re-enable their Pop-up Blocker.