100% Height SidebarSay you want the background and/or border of the sidebar to extend the full height of the page…CSS .container { overflow: hidden; .... } #sidebar { margin-bottom: -5000px; padding-bottom: 5000px; .... } 01234567891011 .container { overflow: hidden; .... } #sidebar { margin-bottom: -5000px; padding-bottom: 5000px; .... }