flex-footer-sticker.css

html{height: 100%;}
 
body{
    display: flex;
    flex-direction: column;
    height: 100%;
}
 
.main{
   /* The main section will take up all the available free space
      on the page that is not taken up by the footer. */
   flex: 1 0 auto;
}
 
footer{
   /* The footer will take up as much vertical space as it needs and not a pixel more. */
   flex: 0 0 auto;
}