You can have TCP and HTTP health checks. A TCP health check will simply check if the web page exists (can be pinged essentially) a HTTP health check needs to return a 200 to pass the health check. More can be found here:
http://stackoverflow.com/questions/23689333/how-to-instruct-an-aws-elb-to-consider-a-health-check-that-returns-a-403-code-as
http://stackoverflow.com/questions/23689333/how-to-instruct-an-aws-elb-to-consider-a-health-check-that-returns-a-403-code-as
