For example, on the site vk.com (not sure if you have to be loged-in or not) when the page is loaded, the first click anywhere on the page causes a pop-up window to flash for a second and (seemingly) disappear. Actually it goes “below” the window (pop-under). I have AdBlock and Ghostery (all checked) installed, and they can’t seem to block that behavior. I can block pop-under’s content with AdBlock, but not the window itself. Though pretty rare but you can encounter this behavior on other sites.
Any ideas how to block that?
Web inspectors says it’s clean
UrlVoid says 3\10 detection
It’s social network site and this behavior started only few days ago.