/var/www rights management

Solution 1:

First, note that your 760 would deny www-data group the permission to "enter" that directory, so it would be unable to serve files from it.

The +s bits on directories force files and subdirectories to be created with the same uid/gid as the directory itself (and subdirectories will also be +s), thus if you

chown user:www-data /var/www/userdir
chmod 6770 /var/www/userdir

any files and folders created in that folder after that point will be user:www-data. Note that you only want to set this on the directories, and it will not "fix" files and directories that already exist.

If you don't need the directory listing or content negotiation features of the webserver, you can leave off the group r bit on the folder (6730). This will make it a little harder to write a script that gets run by the webserver and peeks into another user's directory (they'd have to know the name of the file they want to read). You can also mitigate this by using some form of suexec to make sure that scripts in user directories aren't run in the www-data group.

Solution 2:

Have a look at the Apache2 mod, mod_userdir for the standard approach for user Web directories.