Tomcat and PostgreSQL

[NSB)笠松]

It seems that Tomcat cannot find jdbc Driver,or postgresql.jar.When "http://127.0.0.1:8080/jdbc_servlet/servlet/postgresql_servlet" is accessed, an error message is shown of "java.lang.ClassNotFoundException;org.postgresql.Driver". What do I need to do in order to let Tomcat know the position of postgresql.jar? Please help me out. I have not found any clues for two weeks. Thanks in advance. Hiroshi Kasamatsu