You have access to IIS on your server, but when you try to make changes you get a message saying 'Error: Lock Violation'. This is intended - IIS allows you to prevent changes to some settings. So for example, if you were trying to change an error page, click on the server name in the left hand column of IIS and go to Configuration Editor. Select system.webServer/httpErrors and you may see small padlocks beside some items. Clicking 'defaultPath' and then Unlock Attribute should mean you can then go back to your website and update the error page settings.