function writeIframe()
{
var flag=true;
if(flag)
{
document.write("<div id=\"bmg\" style=\"float:left;z-index:5;position:absolute; left:500px;filter:Alpha(opacity=60);visibility:visible;\"><iframe  src=\"BGM/bgm.htm\"  frameborder=\"0\" scrolling=\"no\" marginheight=\"0\" marginwidth=\"0\"  height=\"20\" width=\"270\" ></iframe></div>");
} 
else
{
document.write("<div id=\"bmg\" style=\"float:left;z-index:5;position:absolute; left:500px;filter:Alpha(opacity=60);visibility:hidden;\"><iframe  src=\"BGM/bgm.htm\"  frameborder=\"0\" scrolling=\"no\" marginheight=\"0\" marginwidth=\"0\"  height=\"20\" width=\"270\" ></iframe></div>");
}
}