Enable logging for a classic asp site

You should install the HTTP Errors feature in IIS. This is enough to view the error message -- you won't need logging.

To install HTTP Errors:

1. Go to the Programs and Features control panel.
2. Select "Turn Windows features on or off"
3. Drill down to Internet Information Services > Word Wide Web Services > Common HTTP Features and select "HTTP Errors" (While you're at it, you can install the logging feature by drilling down to Internet Information Services > Word Wide Web Services > Health and Diagnostics and selecting "HTTP Logging".)
4. Click OK to install.

Once installed, configure IIS to show detailed error messages:

1. In the IIS settings for your site you should now see an Error Pages option. Double-click it.
2. Click Edit Feature Settings.
3. Select either "Detailed errors" or "Detailed errors for local requests..." depending on whether you are doing local development or not.
4. In the IIS settings for your site, double-click the ASP option.
5. Expand Debugging Properties and set "Send Errors To Browser" to true.

You should now see detailed error messages.

IIS logs won't help you because they do not include the detailed error messages.