Facebook notifications problem....!!

First go to Notification Setting.
(click the pop down menu beside the Home ---> click on Account Setting & finally click on Notification which is at left hand site).
If Email frequency is checked then unchecked it.
Now in all notification area you will find various sections like Facebook,photos,videos,events,applications etc whichever sections notification you require just click on Edit option & check the box.
Don't forget to save changes.

Hope this helps.