APEX

Dear experts,

I found a lot of similar question, but I unfortunately does not yet reach an exactly answer about the issue that the following dialog always is displayed when accessing sample application:
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The server oracle at XDB requires a username and password.

Warning: This server is requesting that your username and password be sent in an insecure manor (basic authentication without a secure connection).
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How can I hide the dialog when accessing applications?

My configuration is blow:
Oracle Database 11g (11.1.0.6) Production Enterprise Edtion
Oracle Application Express 3.1
Using 'Embedded PL/SQL Gateway' for HTTP Server

Following the manual, 'http://download.oracle.com/docs/cd/E10513_01/doc/install.310/e10496/toc.htm', I had done the steps below for HTTP Server:
1. connect to db as sys as sysdba
2. run @apex_epg_config c: because Oracle Application Express software was unzipped under c drive like c:\apex
3. run ALTER USER ANONYMOUS ACCOUNT UNLOCK;
4. run EXEC DBMS_XDB.SETHTTPPORT(8080);
(5. Not documented but restart listener and database)

After all required configurations,
1. Log into to http://host:8080/apex/apex_admin
2. Create a workspace, and admin user for the workspace
3. Log into http://host:8080/apex using step2
4. Go to Application Builder, and run pre-installed Sample Application
5. Log into the sample application, and click a link
The dialog always displays when clicking link.

I would appreciate if anyone could give me any suggestions.

Thanks,
Rui