CSS

footer at bottom of body

html, body {
  height: 100%;
}
body {
  display: flex;
  flex-direction: column;
}
.content {
  flex: 1 0 auto;
}
.footer {
  flex-shrink: 0;
}

add footer at bottom of page

#footer {
   position: fixed;
   bottom: 0;
   width: 100%;
   height: 60px;   /* Height of the footer */
   background: #6cf;
}