Ajax标签导航效果(仿网易首页)

function getnews(tagid,x){
   url = "tab/"+tagid+'_'+x+'.html';
//   var loadstatustext="<div class='loading'><img src='images/loading.gif' /> Loading request content, please wait...</div>";
   requestType = tagid;


if(ajccache[url]==null){
   CreateXMLHttpRequest();   

//   getObject(requestType+'_cnt').innerHTML = loadstatustext;
   xmlHttp.onreadystatechange = processRequestChange;
   xmlHttp.open("GET", url, true);
   xmlHttp.setRequestHeader("If-Modified-Since","0");
   xmlHttp.send(null);  
}
else
{  shownews(requestType,ajccache[url]);    }
}

function processRequestChange(){
   // only if xmlHttp shows "complete"
   if (xmlHttp.readyState == 4){
      // only http 200 to process
      if (window.location.href.indexOf("http")==-1 || xmlHttp.status == 200){
         newsstring = xmlHttp.responseText;
         //inject centent to tab-pane
            shownews(requestType,newsstring);
            ajccache[url]=newsstring;    //把已访问的数据缓存下来
      }
   }
}

function shownews(requestType,newsstring){
//<![CDATA[
    responsecont = getObject(requestType+'_cnt');
    responsecont.innerHTML = newsstring;
//]]>
}

function TabNews(tagid,x){
    for (var i=1;i<=7;i+=2) {
         if (i == x) {
            getObject(tagid+i).className="tabactive"+i;
            if(i!=1){
               getObject(tagid+(i-1)).style.display="none";               
               if(i!=7){
                  getObject(tagid+(i+1)).style.display="none";
               }