This page describes how to see the SHOE information on the web page at http://www.cs.umd.edu/users/hendler/index.html
When you are browsing that web page, go to the "VIEW" menu item and "View Source" you will see markup like:
<USE-ONTOLOGY ID="cs-dept-ontology" VERSION="1.0" PREFIX="cs" URL= "http://www.cs.umd.edu/projects/plus/SHOE/cs.html">
<CATEGORY NAME="cs.Professor" FOR="http://www.cs.umd.edu/users/hendler/">
<ARG POS=1 VALUE="http://www.cs.umd.edu/projects/plus/">
<ARG POS=2 VALUE="http://www.cs.umd.edu/users/hendler/">
<ARG POS=2 VALUE="Dr. James Hendler">
which are in HTML format, but aren't using standard HTML tags, and thus didn't show up when you went to the web page.
Those annotations are in a machine readable form. The "Use-ontology" provides a pointer to a web page that has the machine readable details of the terms that are legal to be used. [Note that that page also has both HTML and SHOE on it -- the human readable form you see is reflecting the machine readable form encoded for processing - use view source there to see it.]
When a crawler that is looking for this sort of semantic material comes along, it finds this information (that you don't see) and can use it. The markup can be used for search, sorting, filtering and many other uses.
The SHOE language was the first ontology language linked into HTML and embedded on the web. Technical details are available as are papers, demos, examples and much more. All of this can be found on the SHOE web page . Go ahead, give it a try!