Hey all...

First post on here and I'm experiencing the HTC 8X for the first time after switching from iPhone 4S. Sorry if this has been asked before but it's really bugging me and I could find an answer when I searched. So here it is; Why are my Back, Start and Search buttons randomly flashing/pulsating at me sometimes? I'm almost certain it's a push notification but wondered if it's a email/unread text notification or something from a third party app? I know this should be simple enough to figure out but I just can't pin it down to a definitive answer. Any help?

Oh and as a newbie to Windows Phone (who vowed never ever ever ever to leave iPhone) I've gotta say i'm seriously impressed thus far.