Getting 403 forbidden error when testing REST based interface

Hi Experts,

   I am not using identity management. I have created a simple REST (POST) based interface in PI using Advantco adapter. I have used AAE (ICO).

   Here in REST sender channel I have just configured the "Listening Mode".

   When I test the REST service url (http url) in browser (IE or chrome).I get a pop-up to enter userid/password. After that I get 403 forbidden error.

    I have proper access to PI system as a DEVELOPER.

    Is there any special role or access to be included in addition to DEVELOPER role in PI?

    Am I missing any other configuration?

    The url I am using is:  http://<PI host name>:<port>AdvantcoRESTAdapter/RESTServlet?channel=REST_Sender_GetDN&service=RESTSys

   Please help.