function trim (str) {
  str = this != window? this : str;
  return str.replace(/^\s+/g, '').replace(/\s+$/g, '');
}

function esEmail(s){
  var email_pattern = /^(\w|-|.|ñ|Ñ)+\@([a-zA-Z0-9]|-)+\.(\w|\.)+/;
  var email_result;
  email_result = email_pattern.exec(s);
  return email_result;
}

var capa_actual=null;;
function mostrar_opcion(id){
  if (id!=capa_actual){
    ocultar_opcion()
	capa=document.getElementById(id);
	capa.style.display='block';
	capa_actual=id;
  }
}
function ocultar_opcion(){
  if (capa_actual!=null){
	actual=document.getElementById(capa_actual);
	if (actual) actual.style.display='none';
	capa_actual=null;
  }
}