ingozoell/css-mobile-detection.css

## css-mobile-detection.css
#mobile-detection {	position: relative;	display: none;	z-index: 0; }

@media only screen and (max-width: 600px) {
#mobile-detection { position: relative;	display: none; z-index: -1;}
#page {top:10px; }
}

## css-mobile-detection.html
<body>
<div id="mobile-detection"></div>
...
</body>

## css-mobile-detection.js
var $is_mobile = false; // Global var
if( $('#mobile-detection').css('z-index') == '-1' ) {
    $is_mobile = true;
    }

$(document).ready(function() {
if($is_mobile) {
// Code here ...
}
});
	#mobile-detection { position: relative; display: none; z-index: 0; }

	@media only screen and (max-width: 600px) {
	#mobile-detection { position: relative; display: none; z-index: -1;}
	#page {top:10px; }
	}
	var $is_mobile = false; // Global var
	if( $('#mobile-detection').css('z-index') == '-1' ) {
	$is_mobile = true;
	}

	$(document).ready(function() {
	if($is_mobile) {
	// Code here ...
	}
	});