i use the little icon to the right of all the columns to selectively display only certain columns. when i quit out of mozilla, these preferences are not saved, and i have to reset them evertime i start up. the same thing happens when i use view->my sidebar to get rid of that hideous thing. my guess is that this is a bug, and the UI specifies these settings should be saved. if that's not the case, then i would request a new feature, cause i'm really getting tired of reconfiguring mozilla everytime i start up.
*** This bug has been marked as a duplicate of 69298 ***