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



.bottom  {
/*  vertical-align: bottom;
box-pack:center;  
box-align:center; 
display:-webkit-box;
-webkit-box-pack:center;
-webkit-box-align:center;*/
 position:absolute;
  width:300px;
  height:300px;
  margin-left:-150px;
  bottom:0px;
  left:50%;
}