xen discuss - Mar 2009 - Error 404 when trying to get to an xvm repository that includes a + in its name

I just filed bug 7215.  Here is the workaround:

Symptom:

http://src.opensolaris.org/source/xref/xen-gate/xvm-3.3%2Bsunos.hg/
or
http://src.opensolaris.org/source/xref/xen-gate/xvm-3.3+sunos.hg/

Error 404: File not found!
The requested resource is not available.

Workaround:

Escaping the % character with %25 will do the trick, because the last 
parse step
will get an %2B escape sequence as opposed to a + character (space).

http://src.opensolaris.org/source/xref/xen-gate/xvm-3.3%252Bsunos.hg/