The software used to create this is MagicPoint. The link in the slides is wrong, currently the website is http://member.wide.ad.jp/wg/mgp/
I suspect the software is old and the link hasn't been updated in its source.
The HTML is an export. It's not what the software was really designed to produce. That said, I don't know if the quality of the slides is really any better in the native viewer.
They can be with
% mgp -D <dir> -E png <mgpfile>
:)
Defaults to jpg though.