function isEmailAddress(theElement, nombre_del_elemento )
{
var s = theElement.value;
var filter=/^[A-Za-z][A-Za-z0-9_.]*@[A-Za-z0-9_]+\.[A-Za-z0-9_.]+[A-za-z]$/;
if (s.length == 0 ) return true;
if (filter.test(s))
return true;
else
theElement.focus();
return false;
}

function trim(cadena)
{
	for(i=0; i<cadena.length; )
	{
		if(cadena.charAt(i)==" ")
			cadena=cadena.substring(i+1, cadena.length);
		else
			break;
	}

	for(i=cadena.length-1; i>=0; i=cadena.length-1)
	{
		if(cadena.charAt(i)==" ")
			cadena=cadena.substring(0,i);
		else
			break;
	}
	
	return cadena;
}

function validarCampo(campo){
	objeto = eval (campo); 
	if(trim(objeto.value) == ""){
		objeto.focus();
		objeto.value="";
		return false;
	}else{
		return true;
	}
}