function createRequestObject(){
      var peticion;
      var browser = navigator.appName;
            if(browser == "Microsoft Internet Explorer"){
                  peticion = new ActiveXObject("Microsoft.XMLHTTP");
            }else{
                  peticion = new XMLHttpRequest();
}
return peticion;
}
var http = new Array();
function ObtDatos(url){
      var act = new Date();
      http[act] = createRequestObject();
      http[act].open('get', url);
      http[act].onreadystatechange = function() {
      if (http[act].readyState == 4) {
            if (http[act].status == 200 || http[act].status == 304) {
  		var texto
		texto = http[act].responseText
                    var DivDestino = document.getElementById("DivDestino");
                    DivDestino.innerHTML = "<span id='error'>"+texto+"</span>";                
}
}
}
http[act].send(null);
}
function compUsuario(Tecla) {
     Tecla = (Tecla) ? Tecla: window.event;
     input = (Tecla.target) ? Tecla.target : 
     Tecla.srcElement;
     if (Tecla.type == "keyup") {
          var DivDestino = document.getElementById("DivDestino");
          DivDestino.innerHTML = "<span></span>";
          if (input.value) {
               ObtDatos("lib/comprobar_nick.php?q=" + input.value);
          } 
     }
}