I remember visiting this website once...
It was called Object reference not set to an instance of an object.
Here's some stuff I remembered seeing:
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL:
1. Add a "Debug=true" directive at the top of the file that generated the error. Example:
2) Add the following section to the configuration file of your application:
Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode.
Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario.
[NullReferenceException: Object reference not set to an instance of an object.] ASP.views_shared_ads_dynamicsiteskin_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) +112 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +130 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +245 System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +84 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5273
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1