var net=new Object();
net.READY_STATE_UNINITIALIZED=0;
net.READY_STATE_LOADING=1;
net.READY_STATE_LOADED=2;
net.READY_STATE_INTERACTIVE=3;
net.READY_STATE_COMPLETE=4;
net.ContentLoader=function(url,onload,onerror){
  this.url=url;
  this.req=null;
  this.onload=onload;
  this.onerror=(onerror) ? onerror : this.defaultError;
  this.loadXMLDoc(url);
}
net.ContentLoader.prototype={ 
  loadXMLDoc:function(url){
    if (window.XMLHttpRequest){
      this.req=new XMLHttpRequest();
    } else if (window.ActiveXObject){
      this.req=new ActiveXObject("Microsoft.XMLHTTP");
    }
    if (this.req){
      try{
        var loader=this;
        this.req.onreadystatechange=function(){
          loader.onReadyState.call(loader);
        }
        this.req.open('GET',url,true);
        this.req.send(null);
      }catch (err){
        this.onerror.call(this);
      }
    }
  },
  onReadyState:function(){
    var req=this.req;
    var ready=req.readyState;
    if (ready==net.READY_STATE_COMPLETE){
      var httpStatus=req.status;
      if (httpStatus==200 || httpStatus==0){
        this.onload.call(this);
      }else{
        this.onerror.call(this);
      }
    }
  },
  defaultError:function(){
    alert("error fetching data!"
      +"\n\nreadyState:"+this.req.readyState
      +"\nstatus: "+this.req.status
      +"\nheaders: "+this.req.getAllResponseHeaders());
  }
}