I have 3 web servers and a load balancer in front of them and these servers pointing to 1 domain. Lets say one of web app on the server throws status code except http 200(for example website gives 503 error.). How can I redirect server traffic to the other servers? Can I do it via Load balancer and IIS? If yes how? Thanks.
Yes, that' s a common feature for a load-balancer.
I don't know which load balancer you are using, but you should be able to configure a health check: the load balancer will periodically check the health of the service (HTTP in your case) to determine if a server can actually process incoming requests or if it should be temporarily removed from the pool.