.hero-bkg-animated {
  background: gray url(../images/login_background.jpg) repeat 0 0;
  width: 100%;
  margin: 0;
  box-sizing: border-box;
  -webkit-animation: slide 50s linear infinite;
}

@-webkit-keyframes slide {
    from { background-position: 0 0; }
    to { background-position: -1920px 0; }
}