Entries in the location bar drop down list with a yellow (blue on Mac) star at the right end are bookmarks and those entries can't be removed from the location bar drop down list with the Delete key.<br /> You can remove such a bookmarked item that shows in the list if you open that url in a tab and click the yellow star in the location bar.<br /> This will open the "Edit This Bookmark" dialog and you can click the Remove button to remove the bookmark if you want to remove such a bookmarked entry.<br /> See also: * https://support.mozilla.com/kb/Cannot+clear+Location+bar+history * https://support.mozilla.com/kb/Clearing+Location+bar+history