.main-header {
  position: absolute;
  left: 0px;
  top: 0px;
  width: 100%;
  margin: 0px;
  z-index: 99;
  transition: all 500ms ease;
  -moz-transition: all 500ms ease;
  -webkit-transition: all 500ms ease;
  -ms-transition: all 500ms ease;
  -o-transition: all 500ms ease;
}