Please can anyone tell me what does this eroor means in asp.net ?

Imports System.Data
Imports System.Configuration
Imports System.Linq
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.HtmlControls
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Xml.Linq
Imports System.Collections.Generic


Public Class Myhandler
    Inherits System.Web.UI.Page
    Implements IHttpModule

	Private _page As Page = Nothing

	Private temp As Queue(Of String)
	Public Sub New()
		temp = New Queue(Of String)()
	End Sub
	Public Shadows Sub Init(context As HttpApplication) Implements IHttpModule.Init

		AddHandler context.PreRequestHandlerExecute, New EventHandler(AddressOf context_PreRequestHandlerExecute)
	End Sub


	Private Sub context_PreRequestHandlerExecute(sender As Object, e As EventArgs)

		Dim _httpContext As System.Web.HttpContext = System.Web.HttpContext.Current


		If _httpContext IsNot Nothing Then
			_page = TryCast(_httpContext.Handler, System.Web.UI.Page)

			If _page IsNot Nothing Then

				AddHandler _page.Init, New EventHandler(AddressOf _page_Init)

				AddHandler _page.Load, New EventHandler(AddressOf _page_Load)
			Else
				Return
			End If
		Else
			Return
		End If

	End Sub

	Private Sub _page_Init(sender As Object, e As EventArgs)
		Dim hdnGuid As New HiddenField()
		hdnGuid.ID = "hdnGuid"
		If Not _page.IsPostBack Then
			hdnGuid.Value = Guid.NewGuid().ToString()
		End If
		_page.Form.Controls.Add(hdnGuid)
	End Sub

	Private Sub _page_Load(sender As Object, e As EventArgs)
		Dim h1 As HiddenField = DirectCast(_page.Form.FindControl("hdnGuid"), HiddenField)
		Dim currentGuid As New GuidClass()
		currentGuid.Guid = h1.Value
		Dim _httpContext As System.Web.HttpContext = System.Web.HttpContext.Current

		If temp.Contains(Of String)(currentGuid.Guid) Then
			_httpContext.Items.Add("IsRefresh", True)
		Else
			If Not (currentGuid.Guid.Equals(Nothing) OrElse currentGuid.Guid.Equals("")) Then
				temp.Enqueue(currentGuid.Guid)
			End If
			_httpContext.Items.Add("IsRefresh", False)
		End If
	End Sub
End Class