var browerType = '';

/**
 * 判断是否IE3.0以上的版本
 */
function isIE(){

	if(browerType  == ''){
		if ((navigator.appName == "Microsoft Internet Explorer") && (parseInt(navigator.appVersion) >= 3)){	
			browerType = 'ie';
		} else {
			browerType = 'notie';
		}
	}

	return browerType == 'ie';
}

/**
 * 遍历页面中所有160*15的广告Banner图片
 * 保留第一块显示的，隐藏其他的所有块
 */
function hideAdBanner(){
	var adBanners = getBannerElements();

	if(adBanners == null || adBanners.length == null){
    return;		
	} else{

	  var findFirst = false;
	  for(var i=0;i<adBanners.length;i++){
	  	//alert(i + ":" + adBanners[i].id + ":" + isHidden(adBanners[i]));
	  	if(!findFirst && !isHidden(adBanners[i])){
	  		findFirst = true; 
	  	} else {
	  		if(isIE()){
	  			adBanners[i].style.display = "none";
	  		} else {
	  		  adBanners[i].width = 1;
	  		  adBanners[i].height = 0;
	  	  }
	    }
	  }
  }
}

/**
 * 判断一个对象是否是隐藏的
 * 上溯到若干级，如果是上级是隐藏的则当前一定是隐藏
 */
function isHidden(obj){

	var loopNumber = 0;
	

	var currentObj = obj;
	do{

	  if(currentObj == null || currentObj.style.display == "none" || currentObj.style.visibility == "hidden"){
	  	return true;
	  }
	  

	  currentObj = currentObj.parentNode;
	  

  }while(currentObj.tagName != 'BODY' && (loopNumber++) < 10)

  return false;
}

/**
 * 返回广告图片数组数组
 * 该死的firefox,对象id都拿不到
 */
function getBannerElements(){

  if (isIE()){			    
    return document.all('ad160_15Banner');
  } else{
    var objArr = new Array();
    var index = 0;
    //alert(document.length);
	  for(var i=0;i<document.images.length;i++){  
	    if(document.images[i].src.indexOf('160x15_ad.gif') != -1){
	    	//alert(document.images[i].src);
	      objArr[index++] = document.images[i];
	    }
	  }    
	 
    return objArr;
  }	
}