var ilst = new Array(
	"bg01.css",
	"bg02.css",
	"bg03.css",
	"bg04.css"
);
var rndno = Math.floor((Math.random() * 100)) % ilst.length;
var output ='<link rel="stylesheet" type="text/css" href="../css/' + ilst[rndno] +'">';
document.write(output);