<link rel="stylesheet" media="only screen and (min-device-width: 721px)" href="css/styletab.css">
<link rel="stylesheet" media="only screen and (max-device-width: 720px)" href="css/style.css"
It always defaults to styletab.css. Works on android.
Added (1). <link rel="stylesheet" media="only screen and (max-device-width: 720px)" href="css/style.css" >
Read more: How come the iPhone won't pick this up?