Nag:
When you installed Tomcat, it would have prompted you for an Administrator LoginID & Password. Your inputs are stored in a file called tomcat-users.xml under %CATALINA_HOME%\conf. In case you forgot your adminstrator userid/password, you can always open this ascii file and see it.
Now,
if you just type
http://localhost 
ort/manager, you will be first prompted for the ID/password. Then it response will be blank or
FAIL - unknown command.
The correct syntax to use the manager webapplication is
http://{host}:{port}/manager/{command}?{parameters}
.
One of the commands you can use is list.
You can find more about manager webapp in your tomcat documentation..usually %CATALINA-HOME%\docs\tomcat\manager-howto.html.
Hope this helped to solve your issue