This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Obviously your servlet doesn't implement doGet method, that's why you are getting error while accessing http://localhost:8080/foo/Tester.do through browser.Whenever we access some thing directly on the browser, GET method will be triggered.
So try calling the Tester.do from html page like below then POST will be triggered.