ASP.NET MVC adding error information to your error page for easier debugging during development.

Error.cshtml

@model System.Web.Mvc.HandleErrorInfo

@{
    ViewBag.Title = "Error";
}

<h2>
    Sorry, an error occurred while processing your request.
</h2>

<!-- Don't do this in production!  You don't want peeps seeing stack traces now, do you? -->
<div style="color:white">
    @Model.Exception.Message
    @Model.Exception.StackTrace
</div>