I've come to like the idea of creating a "user group" for my app. So if I have a website/app called "Cowiki", for example, I create a new user and associated group called "cowiki" with a home directory at "/home/cowiki/" under which the site code resides. This could be simple HTML for a static site or a framework's site code (Rails, Phoenix, whatever), internally organized as fits the application/framework.
As I said, I think of these home directories as "user groups". Since they exist as groups in the access settings, I can give actual users permission to the group as needed. For example, maintainers of the site would have full cowiki group access.
The best part of this, and the main reason to do it, is because I always partition my discs such that "/home" is a separate partition (and possibly a separate drive) from "/". That way it is easy to keep my apps backed up, and easily restore a system if the OS needs a reinstall (just don't mount your home partition during install and then switch it over in fstab afterwards -- only trick is to keep user ids the same).
If you keep your web apps in "srv/" you can still get the group benefits by adding a group independent of a adding a new user. But you have to backup "srv/" independently and ideally have yet another partition for it to keep it separate from the OS files. To me that's seems a bit more trouble then it's worth.
/var/wwwand usually have that on another drive (just preference).