What's this?

and am i the only one seeing this prompt?

no. im getting some shit as well now mate.

internet explorer...thats your first problem

What post was doing it?

that's the "undo/redo" option thingy. if you "go advanced", it's next to the paper clip.

oh yeah...duh...if you start to make a reply to a post...it will ask you that to make sure you don't want to leave before you make your post

right on never had it pop up before now.
i like the new changes/fixes btw, i know you riu folks don't get enough credit but i am throwing you some rep on the new looks of the reply message area and the auto-save (stoners like me need auto-save)...keep up the good work.