function showNav(divName,navimgName){
var tempObj=document.getElementById(divName);
var navimg=document.getElementById(navimgName);
var navTd=document.getElementById("navTd");
var bodyDiv=document.getElementById("bodyDiv");
for(i=1;i<=8;i++){
document.getElementById("imgdiv"+i).src=loadImage("../../img/comm/imgdiv"+i+"_r.jpg").src;
document.getElementById("divNav"+i).style.visibility="hidden"
}
navimg.src=loadImage("../../img/comm/"+navimgName+"_b.jpg").src;
navimg.style.cursor="pointer";
tempObj.style.left=bodyDiv.offsetLeft+navTd.offsetWidth+navimg.offsetParent.offsetLeft+navimg.offsetLeft+navimg.width/2-tempObj.offsetWidth/2+"px";
tempObj.style.visibility="visible";
}
function hideNav(divName){
var tempObj=document.getElementById(divName);
tempObj.style.visibility="visible";
}

function scall(){
for(i=1;i<=8;i++){
document.getElementById("divNav"+i).style.visibility="hidden"
}
}
window.onresize=scall;//火狐
window.onload=scall;//IE,重载时隐藏，主要是用于拖动浏览器改变大小时，防止下拉框横坐标错位


var imgCache = {};
	function loadImage(imgSrc) {//图片缓存函数 
		var pageImg = imgCache[imgSrc];
		if(!pageImg) {
			pageImg = new Image();
			pageImg.src = imgSrc;
			imgCache[imgSrc] = pageImg;
		}
		return pageImg;
	}