Code
<style type="text/css">
#box_rel{
background-size:40% 70%;
-webkit-background-size:40% 70%;
-moz-background-size:40% 70%;
}
#box_abs{
background-size:50px 50px;
-webkit-background-size:50px 50px;
-moz-background-size:50px 50px;
}
#box_cover{
background-size:cover;
-webkit-background-size:cover;
-moz-background-size:cover;
}
#box_contain{
background-size:contain;
-webkit-background-size:contain;
-moz-background-size:contain;
}
</style>