hi I am assuming that you have configured and your web server is good to use....
Then follow the steps...
1.create user/www_user in the database to whih you want to connect.
(ofcourse with all privs needed)
2.grant www_user also the privs.
3.go to server run
owsctl start -nodemgr
(it will bring the admin page to create dad,pl/sql cartri.....)
4.open netscape and open the web page giving the page url(say servernameortno)
5.you will get tree...
6.open the tree and click on 1 appln server..../click dad
7.click + button in DAD screen which comes on right side.
8.give all the details it ask and sid colun leave blank and in connecting string give the db sid.
9.enter apply you will get success screen and click ok.
10.click on listeners and add the virtual path needed.and click apply....and ok
11.go to appln in the bottom of the tree...
12.double click it will ask you pl/sql stuff(select from match code)
13.click cartridge and give regd field and click ok.
14.donot forget to remove the wrong entry from config in the same place.
15.stop and start the listner..
16.type the url in netscape for this user you have given in directory(lister)
17.you will get prompt saying connected to database..
hopr it will work.once it done please donoit forget to run owsctl stop -nodemgr command in server.
any doubt pl keep posting.
One addition I would like to make to Tanigai's note here was that, even if you build the Pl/SQL carterige, you have to have the PLSQL tool kit installed into the database to recognize the htp, htf and etc packages. This one is available under Utilities and choose the PL/SQL tool kit and install it into your target database.