I import the WAR file to Eclipse and try to run the server.... i got this error:
" The server does not support version 2.5 of the J2EE Web module specification"
Not sure what you mean by "revert back", but if the web app is written for Servlet API 2.5 then you need a container that supports it - like Tomcat 6. (Tomcat 5 only supports Servlet API 2.4.)
It is clear that your server is not having the latest web container. Please go for the web server which is containing servlet version 2.5. If not able to understand please write again.
right click project -> Properties --> project Facets
change Dynamic Web Module from 3 to 2.4
Next time verify that you set Dynamic Web Module version to 2.4 during Web Module creation
Don't get me started about those stupid light bulbs.