//ShowArry_109, 109表示广告位编号
var ShowArry_109 = new Array();
ShowArry_109[0] = '<a href="showproxy.aspx?a=125" target="_blank"><img src="UploadFile/Admin/image/2012-01-30/634635182443558225.gif" width="270" height="88" ></a>';
//得到广告随机索引
var rnd = Math.floor(Math.random() * ShowArry_109.length);
//输出广告信息
document.write(ShowArry_109[rnd]);