function preload () {
	xImage= new Array (7);
	for (i=0; i< xImage.length; i++) {
		xImage[i] = new Image ();
	}

	//Main Menu Images
	xImage[0].src="images/Introduction_Over.gif";
	xImage[1].src="images/Speaker_Over.gif";
	xImage[2].src="images/Schedule_Over.gif";
	xImage[3].src="images/Map_Over.gif";
	xImage[4].src="images/Direction_Over.gif";
	xImage[5].src="images/Download_Over.gif";
	xImage[6].src="images/History_Over.gif";
}
// swap image when mouse out the button
function SwapImage(img_name,img_src) { 
	eval("document." + img_name + ".src ='" + img_src + ".gif'");
}