The OGRE Manual is built using texi2html from .texi and .inc files in Docs/src.
Unfortunately, texi2html has been through some rough times, and had many interface-breaking changes, changed ownership, and is pretty badly documented. The latest versions will not work with the OGRE manual source because of these breaking changes. So far, I have not been able to make the manual work well with any version of texi2html except version 1.70.
If you are using Mac OS X 10.7 "Lion" then you will already have this version installed.
Fortunately, installing this version is fairly easy. Just grab the source code to 1.70 from here: http://download.savannah.gnu.org/releases/texi2html/ , and make sure you have texinfo already installed using your chosen package system. Then as normal:
./configure && make && sudo make install
After you log out and log back in, you should get this:
steve@superawesome:~$ texi2html -version 1.70
You can now go into ogre/Docsand run:
Note that this will build the Doxygen API reference too.