Common causes of 500 errors are: ASP syntax error, Access database connection statement error, file reference and include path error, use of components not supported by the server such as FSO.
In addition, for win2008 IIS does not display detailed error messages by default the following is the focus, 2008 by default it will not show detailed errors.
1. Open IIS, click on the "error page" in Global settings (note that it must be a global site!)
2. Click Edit Feature Settings in the upper right corner.
2. In the error response, select the "Verbose error" of the second item
3. Click OK to refresh IE will display a detailed error message.
Note: In this setting, you cannot customize the error page to 500 internal errors. It is recommended that you find the error after you modify it back ha.
Causes and workarounds for win2008 500 internal errors that do not show detailed errors