uses
  ActiveX, Jpeg;

procedure WebBrowserScreenShot(const wb: TWebBrowser; const fileName: TFileName) ;
var
  viewObject : IViewObject;
  r : TRect;
  bitmap : TBitmap;
begin
  if wb.Document <> nil then
  begin
    wb.Document.QueryInterface(IViewObject, viewObject) ;
    if Assigned(viewObject) then
    try
      bitmap := TBitmap.Create;
      try
        r := Rect(0, 0, wb.Width, wb.Height) ;

        bitmap.Height := wb.Height;
        bitmap.Width := wb.Width;

        viewObject.Draw(DVASPECT_CONTENT, 1, nil, nil, Application.Handle, bitmap.Canvas.Handle, @r, nil, nil, 0) ;

        with TJPEGImage.Create do
        try
          Assign(bitmap) ;
          SaveToFile(fileName) ;
        finally
          Free;
        end;
      finally
        bitmap.Free;
      end;
    finally
      viewObject._Release;
    end;
  end;
end;