function httpRequestObject(){
var s_err = null;
var o_xmlhttp = null;

	
	try
        {
        // Firefox, Opera 8.0+, Safari
            return    o_xmlhttp=new XMLHttpRequest();
        }
      catch (s_err)
        {
        // Internet Explorer
        try
          {
               return  o_xmlhttp=new ActiveXObject("Msxml2.XMLHTTP");
          }
        catch (s_err)
          {
          try
            {
                  return o_xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
            }
          catch (s_err)
            {
            alert(s_err.message);
            return false;
            }
          }
        }
}


function doAjaxRequest( params , callBack ){

	var http = new httpRequestObject();
	if( http ){
	    http.open( "GET", params , true );	
	    http.send( null );
	    http.onreadystatechange = callBack; 
	}
}