window.onload = setScreenClass; 
	window.onresize = setScreenClass;
 
	//  Following transition classes will be declared:
	//
	//	classname		  screenwidth
	//	------------------------------------------
	//	screen_lo		  <  800px	
	//	screen_med		  800px - 1024px	
	//	screen_hi		 1024px - 1280px	
	//	screen_wide				> 1280px			
 
	function setScreenClass(){
		var fmt = document.documentElement.clientWidth;
		var cls = (fmt<=800)?'screen_low':(fmt>800&&fmt<=1024)?'screen_medium':(fmt>1024&&fmt<=1280)?'screen_high':'screen_wide';
 document.body.className=cls;
	};