If you are testing in IE and have the friendly error messages on you will need to turn this off. To do so go to Tools > Internet Options > Advanced. In here find the 'show friendly http error messages' and uncheck it. You will need to close and reopen your browser to see the changes.
If you are not using IE and are not seeing the friendly error messages then you may be seeing a custom 500 error from your host. If this is the case you will need to have then enable regular error messaging for your account. Let us know how this goes for you.