Switch CSS background instead of resizing it. With media queries

gistfile1.css

html{
	background: url(res/bg/1280.jpg) fixed center black;
}
@media only screen and (min-width:1281px),
       only screen and (min-height:801px) {
	html{ background-image: url(res/bg/1366.jpg); }
}
@media only screen and (min-width:1367px),
       only screen and (min-height:855px) {
	html{ background-image: url(res/bg/1440.jpg); }
}
@media only screen and (min-width:1441px),
       only screen and (min-height:901px) {
	html{ background-image: url(res/bg/1680.jpg); }
}
@media only screen and (min-width:1681px),
       only screen and (min-height:1051px) {
	html{ background-image: url(res/bg/1920.jpg); }
}