ASP.NET

protected void AddToQuoteButton_Click(object sender, ImageClickEventArgs e)
{
  try
  {
    Guid guid = new Guid(Request.QueryString["id"]);
    QuoteManager.AddToQuote(Page, guid);
  }
  catch (Exception ex)
  {
    throw new Exception("Illegal Product Code in query string.", ex);
  }
}

public partial class _500 : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
    if(Server.GetLastError() != null)
    {
      string error = Server.GetLastError().Message;
      ErrorLabel.Text = error;

      Server.ClearError();
    }    
  }
}

<customErrors mode="On" defaultRedirect="~/500.aspx">
    <error statusCode="404" redirect="~/404.aspx"/>
</customErrors>

FirstName 
Lastname 
Address
Zip etc..