I didn't have the browser issue, but somewhat related, I did manage to stop the lousy buggers from visually polluting my Xfce desktop. This may not help your situation, but maybe worth a try. I don't really know if it's connected, though. Good luck.
Hidden files on.
Right click and open the file with gedit.
Add: gtk-enable-tooltips = 0
Save. Log out. Log in.