Following developer steps for getting involved in the ownCloud project, I found on the Code Reviews page
https://doc.owncloud.org/server/9.2/developer_manual/bugtracker/codereviews.html
that the link under Examples
for coding guidelines ends up not being found.
https://doc.owncloud.org/server/9.2/developer_manual/general/codingguidelines
Seems to be missing the ".html" extension
and then it works fine