[CentOS] firefox and D state

Previously when firefox went catatonic to the point that I could not even scroll, its CPU usage had gone to 100%+. Now top tells me that firefox, Web Content (with a space) or sometimes kswap... has process state D, uninterruptable sleep.

Any suggestions on how to deal?

I often have a lot of tabs open, so discovering the right one was hard enough before. Usually, it was something relatively new, so that helped. Not so much anymore. I think a lot of it is just waiting (D) for ads or running them.

Closing and reopening sometimes works, but then I have to go find all the video ads and stop them one at a time.