ranimg = new Array(); 
ranimg[0]="http://harmonia-hp.com/image/bg_logo.png"; 
ranimg[1]="http://harmonia-hp.com/image/bg_logo2.png"; 
ranimg[2]="http://harmonia-hp.com/image/bg_logo3.png"; 
xx = Math.floor(ranimg.length*Math.random()); 
ranimg = ranimg[Math.floor(xx)]; 
document.write ('<style type="text/css"><!--div.clear { background: url("'+ ranimg +'") no-repeat;}--></style>');