Running W3C validator (http://validator.w3c.org) on the index.html page
gives the following error:

    Error: element "NOFRAMES" not allowed here; check which elements this
    element may be contained within

The problem is that <NOFRAMES> must be *inside* the <FRAMESET> element,
and typically follows a <FRAME> element. However, the <NOFRAMES> tag
currently follows the <FRAMESET> element, as shown here:

  10: <FRAMESET cols="20%,80%">
  11: <FRAMESET rows="30%,70%">
  12: <FRAME src="overview-frame.html" name="packageListFrame" title="All Packages">
  13: <FRAME src="allclasses-frame.html" name="packageFrame" title="All classes and interfaces (except non-static nested types)">
  14: </FRAMESET>
  15: <FRAME src="overview-summary.html" name="classFrame" title="Package, class and interface descriptions">
  16: </FRAMESET>
  17: <NOFRAMES>
  18: <H2>
  19: Frame Alert</H2>
  20:
  21: <P>
  22: This document is designed to be viewed using the frames feature. If you see this message, you are using a non-frame-capable web client.
  23: <BR>
  24: Link to<A HREF="overview-summary.html">Non-frame version.</A></NOFRAMES>