var cssurl= new Array();
cssurl[0]="common/css/index_main1.css";
cssurl[1]="common/css/index_main2.css";
cssurl[2]="common/css/index_main3.css";
cssurl[3]="common/css/index_main4.css";
cssurl[4]="common/css/index_main5.css";
n= Math.floor(Math.random()*cssurl.length);
document.write("<link rel='stylesheet' type='text/css' href='"+cssurl[n]+"'>");