Popup Displayed behind Yahoo home page

[Chuckz]

In the last few days, when I shrink the Yahoo home page or sign off, there is at times, an advertisement displayed. Why and how do I block ?

[stephfoster]

Have you scanned your computer for spyware? I haven't been using Yahoo's home page, but it may not be from them. When I checked, I didn't get a popup.

[mmelen]

It's spyware, yahoo wouldn't have popups.