Why does my history pop up from my bookmark bar, it didn't do that before?
When ever I open up my browser my history pops up in a sidebar from my bookmarks bar (like if you pressed the little clock button from the right click, "Customize" on the bookmarks bar) and it hasn't done that before.
Opaite Mbohovái (2)
Window sizes and positions are stored in localstore.rdf in the Profile Folder. There may be a problem with that file if the History sidebar keeps opening if you have closed it before you exit Firefox.
See http://kb.mozillazine.org/Corrupt_localstore.rdf (caution: do not delete the localstore.rdf file in the Firefox program installation folder)
Note: Deleting the file localstore.rdf will reset the customizations of the toolbars to the defaults. You can rename localstore.rdf to localstore.rdf.sav to test if that solves it. Then you can restore the customization by copying localstore.rdf.sav to localstore.rdf if it didn't work.
Maybe you have View > Sidebar set to History? If so uncheck it.