You miss the function that is on the webpage
Copy it also in the module

Like this

Sub Mail_ActiveSheet_Body()
   Dim OutApp As Outlook.Application
   Dim OutMail As Outlook.MailItem
   Application.ScreenUpdating = False
   Set OutApp = CreateObject("Outlook.Application")
   Set OutMail = OutApp.CreateItem(olMailItem)
   With OutMail
       .To = "ron@debruin.nl"
       .CC = ""
       .BCC = ""
       .Subject = "This is the Subject line"
       .HTMLBody = SheetToHTML(ActiveSheet)
       .Send   'or use .Display
   End With
   Application.ScreenUpdating = True
   Set OutMail = Nothing
   Set OutApp = Nothing
End Sub

Public Function SheetToHTML(sh As Worksheet)
'Function from Dick Kusleika his site
'http://www.dicks-clicks.com/excel/sheettohtml.htm
'Changed by Ron de Bruin 04-Nov-2003
   Dim TempFile As String
   Dim Nwb As Workbook
   Dim myshape As Shape
   Dim fso As Object
   Dim ts As Object
   sh.Copy
   Set Nwb = ActiveWorkbook
   For Each myshape In Nwb.Sheets(1).Shapes
       myshape.Delete
   Next
   TempFile = Environ$("temp") & "/" & _
   Format(Now, "dd-mm-yy h-mm-ss") & ".htm"
   Nwb.SaveAs TempFile, xlHtml
   Nwb.Close False
   Set fso = CreateObject("Scripting.FileSystemObject")
   Set ts = fso.GetFile(TempFile).OpenAsTextStream(1, -2)
   SheetToHTML = ts.ReadAll
   ts.Close
   Set ts = Nothing
   Set fso = Nothing
   Set Nwb = Nothing
   Kill TempFile
End Function