<link rel="stylesheet" media="screen and (max-width: 960px)" href="big.css" />
<link rel="stylesheet" media="screen and (min-width: 480px)" href="small.css" />
<!-- для iPhone 4 -->
<link rel="stylesheet" media="only screen and (-webkit-min-device-pixel-ratio: 2)" type="text/css" href="iphone4.css" />
<!-- для iPad portrait and landscape -->
<link rel="stylesheet" media="all and (orientation:portrait)" href="portrait.css">
<link rel="stylesheet" media="all and (orientation:landscape)" href="landscape.css">
так по моему лучше)