var preLoadFlag = "false";

function preLoadImg(URL){
	arrImgList = new Array (
		URL+"images/relation_btn_on.gif",
		URL+"images/aboutus_btn_on.gif",
		URL+"images/forusers_btn_on.gif",
		URL+"images/foradmin_btn_on.gif",
		URL+"images/topics_btn_on.gif"
	);
	arrPreLoad = new Array();
	for (i in arrImgList) {
		arrPreLoad[i] = new Image();
		arrPreLoad[i].src = arrImgList[i];
	}
	preLoadFlag = "true";
}

/* var preLoadFlag = "true"; */

function chgImg(fileName,imgName){
	if (preLoadFlag == "true") {
		document.images[imgName].src = fileName;
	}
}