window.onload = function(){setScreenClass();}; 
	window.onresize = setScreenClass;

	//  Following transition classes will be declared:
	//
	//	classname		  screenwidth
	//	------------------------------------------
	// screen_low       <= 800px
	// screen_low		<= 1024px	
	// screen_high		> 1024px			


	function setScreenClass(){
		var fmt = document.documentElement.clientWidth;
		var cls = (fmt<=800)?'screen_low':(fmt>800&&fmt<=1024)?'screen_med':'screen_high';
		document.body.className=cls;
	};