If you make a request and the client is redirected to Rational DOORS Web Access with the resource displayed, then the resource was valid, but the accept mime type was not present or was not validated. If the client is simply redirected to the Rational DOORS Web Access main page, then the resource was not valid or the request was invalid. Other errors are displayed in the logs if they are using the festival-log4j.xml.support version.
Check the Rational DOORS Web Access logs to see the actual request that was made.
For more information, see the CALM 2009 link rendering specification at https://jazz.net/wiki/bin/view/Main/LinkRendering.