Below is my web.config. I added the cutom error mode = "Off", but still get the same error (or lack of Error) page I pasted above. This site started as the Timetracker starter kit. All but a couple of entries (attributes) on the file was created by MS.
<?xml version="1.0"?>
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
<connectionStrings>
<remove name="LocalSqlServer" />
<add name="LocalSqlServer" connectionString="Data Source=.\SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|TimeTracker.mdf;User Instance=true" />
<add name="aspnet_staterKits_TimeTracker" connectionString="Data Source=.\SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|TimeTracker.mdf;User Instance=true" />
<add name="ConnectionString" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\TimeTracker.mdf;Integrated Security=True;User Instance=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
<system.web>
<customErrors mode="Off"/>
<httpHandlers>
<add path="Reserved.ReportViewerWebControl.axd" verb="*" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
validate="false" />
</httpHandlers>
<siteMap defaultProvider="AspNetXmlSiteMapProvider" enabled="true">
<providers>
<clear/>
<add name="AspNetXmlSiteMapProvider" type="System.Web.XmlSiteMapProvider, System.Web, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" siteMapFile="web.sitemap" securityTrimmingEnabled="true"/>
</providers>
</siteMap>
<authentication mode="Forms">
<forms loginUrl="~/TimeTracker/login.aspx"/>
</authentication>
<compilation debug="false">
<assemblies>
<add assembly="Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
<add assembly="Microsoft.ReportViewer.Common, Version=8.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
</assemblies>
<buildProviders>
<add extension=".rdlc" type="Microsoft.Reporting.RdlBuildProvider, Microsoft.ReportViewer.Common, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
</buildProviders>
</compilation>
<customErrors mode="RemoteOnly"/>
<machineKey decryptionKey="AutoGenerate,IsolateApps"/>
<roleManager enabled="true"/>
</system.web>
</configuration>