function isEmail (campo) {
	email = campo.value;
	if (email == null || email == ""){
		return false;
	}
	var emailPattern = /^(([A-Za-z0-9]+_+)|([A-Za-z0-9]+\-+)|([A-Za-z0-9]+\.+)|([A-Za-z0-9]+\++))*[A-Za-z0-9]+@((\w+\-+)|(\w+\.))*\w{1,63}\.[a-zA-Z]{2,6}$/;
	var matchArray = email.match(emailPattern);
	if (matchArray == null){
		return false;
	}
	return true;
}
function validarFormaLogin() {

	if( !isEmail(document.forma.usuario) ) {
		alert('Proporciona un correo electr\u00F3nico v\u00E1lido');
		document-forma.usuario.focus();
		return false;
	}
	if( document.forma.password.value == '' ) {
		alert('Proporciona la contrase\u00F1a');
		document.forma.password.focus();
		return false;
	}
	document.forma.submit();
	return true;
}