window.onload = function(){


	
	
	
/*  background image
--------------------------------------------------------------------------*/
	var bgClass = new Array(3);
	bgClass[0] = "bg01";
	bgClass[1] = "bg02";
	bgClass[2] = "bg03";
	bgClass[3] = "bg04";

	
	var randBg = Math.floor( Math.random() * (3+1) );
	var randBgClass = bgClass[randBg];
	
	document.getElementById("container").className = randBgClass;
}