The procedure below will add the THead element.

Sub TheadHTMLAdd()
   Dim strHtml As String

   strHtml = _
   vbCrLf & _
   vbTab & _
   vbTab & _
   "<thead>" & _
   vbCrLf & _
   vbCrLf & _
   vbTab & _
   vbTab & _
   "</thead>" & _
   vbCrLf

   'Insert text as first element.
   ActiveDocument.all.tags("table"). _
   Item(0).insertAdjacentHTML _
   "afterBegin", strHtml

   'Save the changes
   WebDesigner.ActivePageWindow.Save True

End Sub				

HTML code before method was run:

  <table>
  </table>						

HTML code after method was run:

  <table>
    <thead>

    </thead>
  </table>	

 

Valid XHTML 1.0 Transitional        Valid CSS!