Cannot access the AWS instance

I have created an instance on AWS. I used Remote Desktop connection to deploy an application on Tomcat. On the remote server, I can use http://localhost/myapp to open and run the application. In the EC2 Console, I edited the Security Groups, i.e., edit inbound rules, and allow HTTP (port 80). However, I still cannot access the application via http://.../myapp (... is the public ip). I have also tried to allow all traffic from anywhere, and it still didn't work.

Can anyone give me any advices? Thanks a lot.