Alternative to Polling. HTML Updates

I am working on a collaborative website that I want to give users notifications while they are viewing or editing data. Something similar to ho开发者_开发知识库w in StackOverflow if you are replying to a question and the notification at the top pops up saying that there is a new reply to the post.

I can see how to do this using some kind of polling AJAX magic, but I was wondering if there was any way to push the notification to the browser w/o using polling?

Thanks for any help/ideas :)

EDIT:

For those interested, I went with SignalR https://github.com/SignalR/SignalR/wiki/Hubs

Either use long polling for it to work in older browsers, or start reading up on eventSource:

http://dev.w3.org/html5/eventsource/

Nice article by Nicholas Zakas:

http://www.nczonline.net/blog/2010/10/19/introduction-to-server-sent-events/

Well im starting to use Websockets (see some of my previous questions) and they are cool to use instead of ajax :-D

Generally no, but there is a family of techniques that simulate such an effect.

Look into comet if you'd like to give it a shot: http://en.wikipedia.org/wiki/Comet_(programming)