Hi Shelley,
As I see, you were configuring it as the same as is described in the DevGuide in the section - Configuring custom error pages, you're doing well!
But try also to configure the Kentico CMS running on a server with IIS 7 the right way, the procedure is quite simple - it consists only of adding and modifying a few keys in your project's web.config file.
Take a look at following page under Optional configuration (recommended) - add a <httpErrors> element into the system.webServer section of your web.config:
http://devnet.kentico.com/docs/devguide/index.html?custom_url_extensions_iis7.htmBest regards,
Martin Danko