function GetXmlHttpObject( handler ) { 
  var objXmlHttp=null;
  
  if( navigator.userAgent.indexOf( "Opera" )>=0) {
    alert( "This example doesn't work in Opera" ); 
    return; 
  }
  
  
  if( navigator.userAgent.indexOf( "MSIE" )>=0 ) { 
    var strName="Msxml2.XMLHTTP";
    if( navigator.appVersion.indexOf( "MSIE 5.5" )>=0 ) {
      strName="Microsoft.XMLHTTP";
    } 
    try { 
      objXmlHttp=new ActiveXObject(strName);
      objXmlHttp.onreadystatechange=handler; 
      return objXmlHttp;
    } catch( e ) { 
      alert( "Error. Scripting for ActiveX might be disabled" );
      return; 
    } 
  }
  
  if( navigator.userAgent.indexOf( "Mozilla" )>=0 ) {
    objXmlHttp=new XMLHttpRequest();
    objXmlHttp.onload=handler;
    objXmlHttp.onerror=handler; 
    return objXmlHttp;
  }
}