Click once in the box. Press a letter. Using your arrow keys, highlight what you want to remove, and press Delete.

In the address bar, type about:preferences#privacy<enter>. Under History select Use Custom Settings.

Near the bottom, look for Clear history when Firefox closes and turn it on. To its far right, press Settings.

Place a mark on everything you want cleared when Firefox closes.

See also:

• https://support.mozilla.org/kb/Clearing+Location+bar+history
• https://support.mozilla.org/kb/Cannot+clear+Location+bar+history

You can check for problems with the places.sqlite database file in the Firefox profile folder if you keep having problems with removing website history.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/