Private Sub AddDivMessage()
    Dim CurrentUri As New Uri(WebBrowser1.Url.ToString())
    Dim HostName As String

    ' Ensure we have a host name, and not just an IP, against which to test.
    If (Not CurrentUri.HostNameType = UriHostNameType.Dns) Then
        Dim Permit As New DnsPermission(System.Security.Permissions.PermissionState.Unrestricted)
        Permit.Assert()

        Dim HostEntry As IPHostEntry = System.Net.Dns.GetHostEntry(CurrentUri.Host)
        HostName = HostEntry.HostName
    Else
        HostName = CurrentUri.Host
    End If

    If (Not HostName.Contains("adatum.com")) Then
        AddTopPageMessage("You are viewing a web site other than ADatum.com. " & _
            "Please exercise caution, and ensure your web surfing complies with all " & _
            "corporate regulations as laid out in the company handbook.")
    End If
End Sub

Private Sub AddTopPageMessage(ByVal Message As String)
    If (WebBrowser1.Document IsNot Nothing) Then
        With WebBrowser1.Document
            ' Do not insert the warning again if it already exists. 
            Dim ReturnedElems As HtmlElementCollection = .All.GetElementsByName("ADatumWarningDiv")
            If (Not (ReturnedElems Is Nothing) And (ReturnedElems.Count > 0)) Then
                Exit Sub
            End If

            Dim DivElem As HtmlElement = .CreateElement("DIV")
            DivElem.Name = "ADatumWarningDiv"
            DivElem.Style = "background-color:black;color:white;font-weight:bold;width:100%;"
            DivElem.InnerText = Message

            DivElem = .Body.InsertAdjacentElement(HtmlElementInsertionOrientation.AfterBegin, DivElem)
        End With
    End If
End Sub