I use Firefox to browse websites such as the UK Daily Mail. Hey, I often get better, more accurate information on breaking news from DM than I do from major media in the US.
Lately, however, the DM pages have started pushing a popup video window on the right side of my browser window, with the title "Watch the whole video". This usually doesn't appear until I have begun scrolling the web page, and then it hangs my browser for a few seconds while it's delivering the popup. The popup then blocks content on the screen, requiring me to press the "CLOSE X" link in the popup's upper right corner.
This popup is not to be confused with the same video "embedded" inline in the web page. I don't mind the embedded video but I definitely am not pleased with the popup window. And it's not an ad. It's another link to whatever video that article is trying to promote.
This popup feels new to me, like it started appearing about a month ago or so.
How can I stop this from appearing and blocking content in my browser?