By default, Oracle HTTP Server (OHS) 11gR2 uses port 8888 for HTTP connections. You can change the listen port for OHS inside the httpd.conf (it should be located in %ORACLE_INSTANCE%\config\OHS\%ohs_instance%). IMPORTANT: Before making any changes to httpd.conf, be sure to make a backup.
Once you have httpd.conf open, look for the section called "#OHS Listen Port". You will notice the line "Listen 8888". Comment that out with a pound # sign. In the line below it, type Listen 80. This will enable OHS to use the standard HTTP port 80. After you have done this, save and close httpd.conf and restart the OHS instance using OPMN. After this is done, you should be able to run the "http://mihost.dominion.com/test" URL without using a port number.
NOTE: If you apply the steps above and it still fails, clear your browser cache and start a new browser session. Hope this helps!