Web User control and Marshelling b/w client browser and web server(database).

[Al]

hi, I am new to asp.net. I have a question about
Marshelling b/w client browser and web server(database). I
heared that it is better to minimize going back and forth
b/w client browser and the server.This will increase
performance and improve scallability.
With asp.net, using server controls. It seems every action
at the client browser require a trip to the server, for
instance, page_load ( to fill combo boxes), or the event
of the combo boxes to fill other dependant combo box. or
when using the server validation controls.
What I am trying to get into is that how come asp.net
development favour using web server controls
[runat="server] even when there is cost (lots of
marshelling b/w client browser and the server)
Or my thinking is wrong.
I would appreciate your feedback to make things clear to
me.
thanks
Al