There seems to be a class of questions which falls between the cracks.
If it is to do with .net or php then it is a SO question If it is apache IIS or general server/network configuration it is a SF question.
There is another class of question which is to do with the day to day running of websites which I would have thought would have been the domain of SU, but there has been a tendency to call these questions "not computer related"
http://superuser.com/questions/25565/how-can-i-take-my-revenge-on-a-spamming-website-closed http://superuser.com/questions/11818/what-is-a-good-free-blogging-site-closed http://superuser.com/questions/13747/how-to-i-sell-ad-space-on-my-website/13761
I think there are lots of other cases where the questions are answered and give value.
Is there an official line on this? Is it determined on a case by case basis, or are websites by their very nature computer related?
(bias update: I probably think they are relevant as I run websites and think the subject is interesting)