How to reload page on a server event?

[Pavel Gusak]

Hello.

I'm writing an ASP.NET web application for users that monitor events.
So, when an event occurs on server (actualy, when a customer places an
order), the users should see this event in their browsers. So, I need to
reload their pages somehow.

What would you recommend to solve the problem?

My ideas:
1. Auto-refresh with some interval: bad, too many extra reloads.
2. Not an ASP.NET-application (Usual thick client with some kind of
callback): better, but requires .NET to be installed on each user's
computer.
3. ?

For method 2 -- what is .NET preferred way of such notification through
Internet?

Thank you.