have you setup the inbound traffic rules to allow your machine to access the AWS environment?
first step is to check the external ip address that is used for your machine/network - http://checkip.amazonaws.com/
if you can ping the machine - you should be good to go. if not - you will need to edit the security group that is used and add an inbound rule for the ipaddress/range that needs to access the system
Actually URL is not working when I stopped the two EC2 instance (to avoid AWS fee in idle time) and re-start them. Is there any care I need to take before doing it? Please let me know
it is most likely that the ip addresses for the machines are diferent on re-start, unless they have been setup with a static ip address