i'm writing this website with flask, and it's a single html thing, with divs that are hidden and shown depending on what tab you want to see, however, i need a div that's an horizontal bar at the bottom of the page, and it's supposed to stay on the bottom of the page regardless of which divs are being shown (currently, if none of the divs are shown), this horizontal bar i made doesn't sit at the bottom of the page. i'm not familiar at all with css, i'm using w3-css though.