this url ,
http://localhost:8080/manager/html will redirect you to the manager page, but this required the authentication , which done against the the data from conf/tomcat-user.xml file. So , you may have to SET the user name and password into POST request to above URL. I never done so , but give it a try , other wise you ask to tomcat community ! and this
http://localhost:8080/docs/manager-howto.html docs may help !
[ July 28, 2008: Message edited by: Sagar Rohankar ]