CustomError not working properly

I have 2 projects named Webproject and Kefi and in the webconfig i have the
same configuration below for the 2:-
<customErrors defaultRedirect="error.aspx"
mode="On">
<error statusCode="500" redirect="error.aspx" />
<error statusCode="404" redirect="error.aspx"/>
</customErrors>



http://localhost/Webproject/error.as...ject/Show.aspx -
this doesn't work
http://localhost/Kefi/error.aspx?asp...fi/Offers.aspx - this
works well and get to the error page

The error i get with the one that doesn't work is:-


Server Error in '/Webproject' Application.
--------------------------------------------------------------------------------

Runtime Error
Description: An application error occurred on the server. The current custom
error settings for this application prevent the details of the application
error from being viewed.

Details: To enable the details of this specific error message to be viewable
on the local server machine, please create a <customErrors> tag within a
"web.config" configuration file located in the root directory of the current
web application. This <customErrors> tag should then have its "mode"
attribute set to "RemoteOnly". To enable the details to be viewable on
remote machines, please set "mode" to "Off".

<!-- Web.Config Configuration File -->

<configuration>
<system.web>
<customErrors mode="RemoteOnly"/>
</system.web>
</configuration>

Notes: The current error page you are seeing can be replaced by a custom
error page by modifying the "defaultRedirect" attribute of the application's
<customErrors> configuration tag to point to a custom error page URL.

<!-- Web.Config Configuration File -->

<configuration>
<system.web>
<customErrors mode="On" defaultRedirect="mycustompage.htm"/>
</system.web>
</configuration>