I am using tomcat and it runs on port 8080 and how can I configure it in my vps server to view my jsp page as default...tomcat always runs in some port?
Switching Tomcat's port to 80 in
server.xml would require root or some other super user to run the Tomcat process since 80 is a privileged port (< 1024). Please don't do this.
There are several threads on ServerFault discussing your question which you might want to take a look at. Using
iptables to pre-route requests from port 80 to 8080 was the least invasive one, I think. But YMMV.