@mixin vertical-gradient($start, $stop) {
  background: $start;
  background: -moz-linear-gradient(top,  $start 0%, $stop 100%);
  background: -webkit-linear-gradient(top,  $start 0%,$stop 100%);
  background: linear-gradient(to bottom,  $start 0%,$stop 100%);
  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='$start', endColorstr='$stop',GradientType=0 );
}