mono ubuntu Runtime Error A runtime error has occurred - asp.net

Question

my web.config is as
<?xml version="1.0" encoding="utf-8"?>
<!--
Web.config file for first.
The settings that can be used in this file are documented at
http://www.mono-project.com/Config_system.web and
http://msdn2.microsoft.com/en-us/library/b5ysx397.aspx
-->
<configuration>
<system.web>
<compilation defaultLanguage="C#" debug="true">
<assemblies>
<add assembly="System.Net, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
<add assembly="System.Data.Services.Client, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
</assemblies>
</compilation>
<customErrors mode="Off"/>
<authentication mode="None">
</authentication>
<authorization>
<allow users="*" />
</authorization>
<httpHandlers>
</httpHandlers>
<trace enabled="true" localOnly="true" pageOutput="false" requestLimit="10" traceMode="SortByTime" />
<sessionState mode="InProc" cookieless="false" timeout="20" />
<globalization requestEncoding="utf-8" responseEncoding="utf-8" />
<pages>
</pages>
</system.web>
<system.webServer>
<handlers>
<remove name="ExtensionlessUrlHandler-Integrated-4.0" />
<remove name="OPTIONSVerbHandler" />
<remove name="TRACEVerbHandler" />
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
</handlers>
</system.webServer>
</configuration>
when I run it
it gives me an error like \
Application Exception
Runtime Error
A runtime error has occurred
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 (for security reasons).
Details: To enable the details of this specific error message to be viewable, please create a tag within a "web.config" configuration file located in the root directory of the current web application. This tag should then have its "mode" attribute set to "Off".
<!-- Web.Config Configuration File -->
<configuration>
<system.web>
<customErrors mode="Off"/>
</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 configuration tag to point to a custom error page URL.
<!-- Web.Config Configuration File -->
<configuration>
<system.web>
<customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
</system.web>
</configuration>

Answer 1

A quick search using Google reveals:
CustomErrors mode="Off"
Basically you need to adjust a few other settings