In your browser, try going to the following URL based on the schema of the database provider you have registered.
In 10.1.4 portal;
For example the default portal schema and portal dad in 10.1.4 is shipped with the name portal. then, you can access this in the browser. Please be mindful of the case in the stem of the URL (portal/pls/portal) which must be in lower-case.
I assume that you want to test out both the functionality of your provider's test page and the connectivity from database server to your application server running your provider?
What always works great for me is the utl_http.request procedure in the database :
1. Connect to your Portal repository database with either SQL*PLUS or any other tool from which you can run SQL / PL/SQL statements
2. Execute the utl_http.request procedure with your provider's test url as argument :
SQL> select utl_http.request('http://www.acme.org/portalTools/omniPortlet/providers/omniPortlet') from dual ;
This will test whether the Omniportlet provider is working and whether it can be reached from the database server.
Hope this helps,