Where to get a pop-up blocker and how to add it to my yahoo toolbar?

The pop up blocker is built into most Internet browsers, like Internet Explorer (the default browser that comes with Windows), Netscape, Safari (for Mac users). But it can be turned on and off, as well as being set to allow pop-ups from certain websites, but to stop them from other sites. If you're using Internet Explorer, then you can turn on the pop-up blocker by going on the menu bar to Tools -> Pop-Up Blocker. That will allow you to turn the blocker on or off. If you're using another internet browser, then you'll have to check how to turn that feature on or off, in that program's Help section.