CXMLDocument *document = [[[CXMLDocument alloc] initWithXMLString:responseString options:0 error:nil] autorelease];
    NSArray *nodes = [document nodesForXPath:@"//data" error:nil];
    for (CXMLElement *xmlElement in nodes) {
        NSLog(@"XML: %@", xmlElement);
        NSString *value = [[[xmlElement elementsForName:@"status"] objectAtIndex:0] stringValue];
        if (value == @"error")
        {
            UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:@"Error"
                                                                 message:@"Los datos ingresados no coinciden"
                                                                delegate:nil
                                                       cancelButtonTitle:@"OK"
                                                       otherButtonTitles:nil];
            [errorAlert show];
            [errorAlert release];
        }
        else {
            NSLog(@"Status: %s", value);
        }

    }