In Windows server 2008, displaying detailed error is disabled by default. To enable this please follow this steps-

1. Open web.config file located under domain root (possibly under wwwroot if helm/DNP, httpdocs if plesk).
2. Look for the lines (esp at last)-
</handlers>
</system.webServer>
</configuration>

after  </handlers>  press enter and add the following line

<httpErrors errorMode=”Detailed”/>

After adding should look like-

</handlers>
<httpErrors errorMode=”Detailed”/>
</system.webServer>
</configuration>
Save the file and now you will be able to see the detailed error.