As Zack Weinberg and Ian Hickson pointed out in http://groups.google.com/group/mozilla.dev.platform/msg/cbc7a15a35143799 , the script that generates the split HTML5 spec doesn't seem to remove files that it no longer generates.  (Ideally, it would add appropriate redirects, but having a 404 is probably better than having out-of-date content.)  This affects both the editor's draft and the TR page copy of the HTML5 spec.

For example, in the TR page copy:
http://www.w3.org/TR/2011/WD-html5-20110525/video.html#video
and
http://www.w3.org/TR/2011/WD-html5-20110525/the-iframe-element.html#video
are the same section of the spec, but the first is out of date (and the only hints that it is out of date are (1) that it's got "Editor's draft" on the side and (2) that it's not reachable from the table of contents.  The same problem exists in the editor's draft at:
http://dev.w3.org/html5/spec/video.html#video
http://dev.w3.org/html5/spec/the-iframe-element.html#the-video-element

However, if somebody has a bookmark to a section of the spec, they won't notice that their bookmark is out of date.

When sections are no longer generated by the splitter, they should be removed (with 'cvs remove <file>; cvs commit <file>', I suspect).  Ideally, they should be redirected (by simultaneously adding to an appropriate .htaccess), but if that's hard, then a 404 should be returned.