When my phone is connected to Wifi,even then i dont get notification if someday pokes me in facebook.How to choose as a background task "allowed"
Windows Phone 8 by turns off your WiFi when the screen turns off to save battery. It automatically reconnects every now and then to check for incoming messages, but that's far from real-time. To keep your WiFi on even when the screen is off, go to Settings->WiFi->More->Keep WiFi on after screen timeout (note: off the top of my head, not the actual words from the operating system). Keep in mind that this will drain your battery faster unless you disable 3G while connected to WiFi.