The problem is although it appears as if it is a pop up, it is actually just HTML giving the impression it's a pop up. It is often called an overlay. Meaning on some sites, it will be junk (as per the screen shot), but other sites very much required (like a shopping basket preview screen).
For FireFox and Chrome, there is a plugin called
BehindTheOverlay which may give you what you want (similar to AdBlocker but for overlay). Chrome also has an extra plugin called
overlay blocker. It is not perfect for many reasons and as already mentioned, do it at your own risk (as it may stop some sites working as intended).
Lastly, AdBlock plus may be able to help as it can be customised, see this forum for more detail https://adblockplus.org/forum/viewtopic.php?t=18595