PostgreSQL has extremely helpful online documentation. I wonder about the various ways to link to the manual.
And there is the URL for to the latest release at any given time, static or interactive:
The pattern of the links has been stable for years. For any given link you get the corresponding chapter in another version by substituting the version number or 'current' (unless the feature has been dropped):
The /interactive branch is now permanently available. (There were dead links for old versions at first.)
Since December 2011 the development docs have been relocated to fit into this regime:
(no /interactive branch)
What to use?
More often than not I can link to a chapter of the manual in my answers.
As long as you have to refer to a specific version this question does not apply. But if the answer isn't version-specific or the version is unknown, then you have to pick. So far I mostly use http://www.postgresql.org/docs/current/static/. A gotcha with that is, when you start at /current and browse the manual, you end up at /9.1 or whatever is current. When you copy the link then you have to edit in '/current' again.
Its amazing how few people even mention their program version in questions. On a programmer's site you'd think they know better.
Considering bit rot, should somebody who looks at an answer three years from now get the manual for the same or the then current version?
Should authors who care follow a canonical way?
What warrants an edit on somebody else's posts?
Do you even think it matters much?
What's your rationale?
I guess this goes on meta, not main - even if the tag postgresql is not available here. The question is aimed at SO, but applies to any site, really, where PostgreSQL is on topic. There must exist related considerations for other projects?