The newest edition of Firefox has this 'feature' that allows tabs to be moved to new windows but it jumps all the time so sometimes you select a tab and it opens in a new window. There is no default option to correct this behavior so I'm using Disable Detach 2 which immediately puts it back to the original window. Maybe someone will find this handy.
Thanks, this can be really useful since ads usually come in new windows which can hog memory once spammed. Firefox should at least have some kind of option to turn off and on their features by your will.