This seems to be a cardinal sin that many web sites are committing. In order to prevent any potential security issues or accidentally divulging the system architecture, all systems that are LIVE should not display the verbose error messages that are used for the developers’ debugging purposes.
If you just want to check out some of these errant sites, just click here (courtesy of Bing). While most of the error messages may not reveal much and may not compromise security, why tempt fate?