How to notify a user of update?

I've developed a web form application in Visual Studio 2012. However, i'm trying to make it better than it is now as it is part of my major project. I'm hoping to allow my webapp to notify user of any update on any page in my webformapplcation. I'm hoping it to be like facebook where it will push a notification where it says there's an status update. May i ask how do i do that?  Any guide or reference would be greatly appreciated. I heard of something called push notification, is that usable? 
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