locking and web interfaces

Hi, I'm fairly new to this subject.

How does locking work when accessing the database via web interfaces?
Usually applications work in a browsing mode. When you click the edit
button, the same data is presented in a form which can be submited for
update.
Is that necessary? If we don't consider the security problems of being
in 'edit mode' all the time, do we need to keep switching between modes?
And what I really want to know is that being web interfaces stateless,
whatever builtin locking you implement it will drop as soon as the web
server is done.
Would persistent connections fix this? Do people use this mode switching
to implement their own locks?

Any pointers to literature on this?

Thanks.

PS: Should I send this to SQL? Whats the policy on cross-posting?

--
Dado Feigenblatt Wild Brain, Inc.
Technical Director (415) 216-2053
dado(at)wildbrain(dot)com San Francisco, CA.