anchor.diff:      (Name: 'pt'; Factor: 0.75; IsAbsolute: True),
       (Name: 'px'; Factor: 1.00; IsAbsolute: True),
       (Name: 'pc'; Factor: 9.00; IsAbsolute: True),
  -    (Name: 'in'; Factor: PixelsPerInch       ; IsAbsolute: True),
  -    (Name: 'cm'; Factor: PixelsPerInch / 2.54; IsAbsolute: True),
  -    (Name: 'mm'; Factor: PixelsPerInch / 25.4; IsAbsolute: True),
  +    (Name: 'in'; Factor: HTMLViewerPixelsPerInch       ; IsAbsolute: True),
  +    (Name: 'cm'; Factor: HTMLViewerPixelsPerInch / 2.54; IsAbsolute: True),
  +    (Name: 'mm'; Factor: HTMLViewerPixelsPerInch / 25.4; IsAbsolute: True),
       // css font sizes
       (Name: '';          Index:  3; IsAbsolute: True),
       (Name: 'smaller';   Index: -1; IsAbsolute: False),
  
positive.code:     if TryStrToLenthUnit(U, LU) then
        with CUnitInfo[LU] do
          if IsAbsolute then
            Result := V * Factor * PointsPerPixel
          else
            Result := V * Factor * Base;
    end
  
negative.code: const
  // CSS 2.1 defines a fixed ratio between pt and px at 96 dpi: 1px = 0.75pt.
  // (see http://www.w3.org/TR/2010/WD-CSS2-20101207/syndata.html#value-def-length for details).
    HTMLViewerPixelsPerInch = 96.0; // fixed assumption in CSS 2.1 as lots of designs rely on it.
    HTMLViewerPointsPerInch = 72.0;
    HTMLViewerPointsPerPixel = HTMLViewerPointsPerInch / HTMLViewerPixelsPerInch;
  
  type
    ThtLengthUnitInfo = record
  