FYI. In recent versions, at least on Ubuntu Unity, the auto-completion selection list is frequently poorly positioned, that is not immediately below or above the input field with the focus. Sometimes the auto-completion selection list is positioned right on top of the input field, so the user cannot see what is being typed. Sometimes the auto-completion selection list is positioned in an apparently random location far from the input field. In the latter case mouse selection does not work because the browser incorrectly determines which item the cursor is on top of because it is apparently using where it "thinks" the selection list is located rather than actually where it is located. Only occasionally is the selection list correctly positioned. Firefox 50.1.0 on Ubuntu 16.04 LTS.