Is there any way to block javascript pop-overs in Firefox or Chrome? [duplicate]

Like the kind pointed to in this image

Many sites have these, and I find them highly annoying. Often you'll be reading an article and suddenly the pop-over blanks out the page and asks "WOULDN'T YOU JUST LOVE OUR EMAIL NEWSLETTER?!" - why no, no I wouldn't.

I'd love to get rid of these if possible.

I'm using FF 38.01 in Win 7 x64.

Yes and no. Yes, they can be blocked quite easily using Adblock Plus or whatever, even Stylish will do.

However, there is no universal way of blocking them. Each site would name their elements differently and telling a legitimate/wanted fixed element from an unwanted one programmatically would be very difficult and very error-prone.

So nothing short of completely disabling JavaScript would help, and even then they could appear; it’s pure CSS, after all.