HeavyFrost,
As mentioned those errors are generic server errors. However in IIS you can use error handling to see the actual errors, here is a link to Microsoft site showing how to use error handling.
How to Use HTTP Detailed Errors in IIS 7.0
http://www.iis.net/learn/troubleshoot/diagnosing-http-errors/how-to-use-http-detailed-errors-in-iis
hope it helps.
Regards,
Alva