function clean(obj,txt){
  if(obj.value=='') {
    obj.value=txt;
  } else if (obj.value == txt) {
    obj.value = '';
  }
}

function Enviar(){
  new Ajax.Request('/inc/Enviar.php',{
    method : 'post',
    parameters : $('FrmContato').serialize(true),
    onCreate:function() {
      $('Enviar').innerHTML = "Aguarde...";      
		},
    onComplete:function(transport) {
      $('Enviar').innerHTML = "Enviar";
      window.alert(transport.responseText);
    }
  });
}