In writing this I discovered / learned about pop-unders!!! Here is what I started with. My popup box is checked. I reviewed Mozilla popup info page. https://support.mozilla.com/en-US/kb/pop-up+blocker Is it a Mozilla popup or another? So I ran virus and malware scans. I thought is was a Mozilla popup as it says "Screensavers - Mozilla Firefox" on the top bar, but I forgot to check the Firefox logo The link to click for the screensaver is -- http://cdn.optmd.com/V2/41975/140046/index.html?g=AQAAu88=&r=www.convertunits.com/from/MB/to/GB. However, I happened to miss part of the link and ended up at this page regarding "pop-unders" http://www.optmd.com/ Seems there is an "opt-out"