function top_random() {
ranimg = new Array();

ranimg[0]="/chikusa/image/top_pict_bg1.jpg";
ranimg[1]="/chikusa/image/top_pict_bg2.jpg";
ranimg[2]="/chikusa/image/top_pict_bg3.jpg";
ranimg[3]="/chikusa/image/top_pict_bg4.jpg";
ranimg[4]="/chikusa/image/top_pict_bg5.jpg";
ranimg[5]="/chikusa/image/top_pict_bg6.jpg";


xx = Math.floor(ranimg.length*Math.random()); 
ranimg = ranimg[Math.floor(xx)]; 
document.write("<style type='text/css'><!--#index #wrapper{background: url('"+ ranimg +"') no-repeat center  0;}--></style>");
}