html { 
  background: url(mainpage.jpg) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

#mainlogo { position: absolute; 
            top: 120px;
            opacity: 0.7;
            decoration: none;
			}