var keepAliveImage = null;   
function KeepAlive(){   
    if(!keepAliveImage) {   
		keepAliveImage = document.createElement("img");   
		keepAliveImage.setAttribute("src", "/images/trans.gif");   
		keepAliveImage.style.position = "absolute";   
		keepAliveImage.style.height = "1px";
		keepAliveImage.style.width = "1px"; 
		document.appendChild(keepAliveImage);  
    }  
    else {  
		var d = new Date();  
		var rand = d.getTime();  
		keepAliveImage.src = "/images/spacer.gif?d=" + rand;  
	}  
}  
setInterval('KeepAlive();', '900000');