Apologies if this issue has been addressed, but I couldn't find it while searching. (Apparently, the search engine strips out underscores.)
When I upgraded to Leopard, it appears that some existing users and groups were renamed. In particular, the old "www" user is now "_www". Everything still worked, so I just rolled with it.
The problem, however, is that the "Sharing & Permissions" part of the Get Info window no longer lets me select _www as a user when I am changing permissions. The "_www" user doesn't show up in the list of users to choose from. It mostly just shows the users you see when you go to "Accounts" in the System Preferences, and all your address books.
How do I get the "_www" user selectable as a user in Get Info?
(I know how to change permissions from Terminal with chmod/chown, but it was a lot more convenient to be able to just do it directly with Get Info.)