A promising idea is to work with the HTML5 notification API; it's perfect if you want notifications to pop on the user screen as long as his browser is running (even if you're surfing another website or if all windows are closed).
http://www.paulund.co.uk/html5-notifications
However, if what you want is to update different parts of your page asynchronously (without refreshing or pushing a button), you should use together :
- Ajax calls;
- Listeners and observers.
When you Ajax calls retrieve particular types of json data (for example), it can trigger appearance of a badge (listener) with a number of new notifications, or so...
With JQuery installed, you should be fine...
Even though it's often not the case, sometimes, for simple tweaks, it's easier to code the job done...
You can start here :
How implement a "observer" in Jquery without plugins? (it's old, but interesting)
Or see this page :
browser instant updates with ajax/jquery
(incredible how often google queries return stacko' pages)