Sticky footer in CSS

sticky-footer.css

# Source: http://tutorialzine.com/2016/03/quick-tip-the-best-way-to-make-sticky-footers/

html {
    height: 100%;
}

body {
    display: flex;
    flex-direction: column;
    height: 100%;
}

header {
   /* We want the header to have a static height, 
   it will always take up just as much space as it needs.  */
   /* 0 flex-grow, 0 flex-shrink, auto flex-basis */
   flex: 0 0 auto;
}

.main-content {
   /* By setting flex-grow to 1, the main content will take up 
   all of the remaining space on the page. 
   The other elements have flex-grow: 0 and won't contest the free space. */
   /* 1 flex-grow, 0 flex-shrink, auto flex-basis */
   flex: 1 0 auto;
}

footer {
   /* Like the header, the footer will have a static height - it shouldn't grow or shrink.  */
   /* 0 flex-grow, 0 flex-shrink, auto flex-basis */
   flex: 0 0 auto;
}