This is the notification that pops up from the App Store on Mountain Lion:
As you can see, the only options are Details and Update. Most of these banners have a 'close' button, to dismiss the notification without taking an action. On this one though, it seems like the only action I can take is opening the App Store with it.
Just clicking the x in the Notification Center list doesn't get rid of this actual notification.
How can I close this without taking the time to open up the App Store?
Best Answer
To dismiss the notification temporarily:
Click and hold the banner and flick it to the right to put that notification in Notification Center. If you are using a Trackpad, You can hover over the alert and use two fingers to flick it to the left.
The notification will still remain in the Notification Center until you update.
Unfortunately, there is currently no way to dismiss the notification permanently.