ZapFixed

great extension. there are only 3 little things it lacks to be perfect: 1: if it remembers its state globally across tabs and restarts, so if you open a new site it hides headers automatically until you click on it again. 2: if there was an option to lock headers instead of hiding them. 3: a public project page on github or other platforms. i think this has the potential to be among the most popular extensions.