try{
    xmlhttp = new XMLHttpRequest();
}catch(ee){
    try{
       xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
       try{
          xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
       }catch(E){
          xmlhttp = false;
       }
    }
}



function abretxt(arquivo){
    //Abre a conexão
    xmlhttp.open("GET",arquivo+".php");
    xmlhttp.onreadystatechange=conteudotxt
    //Executa
    xmlhttp.send(null)
}


function conteudotxt() {
if (xmlhttp.readyState==4){
   //Mostra o HTML recebido
   document.getElementById('ajaxnews').innerHTML=xmlhttp.responseText
   }
}