If you are using a third party application of WhatsApp ie. WhatsApp+ Plus then there is a bad news for you!! WhatsApp is now temporarily banning users who is using WhatsApp+ Plus as it is against WhatsApp ToS (Terms of Service) to use WhatsApp+ Plus.
This is what some users are seeing after getting temporarily banned :
How to avoid getting temporarily ban?
Update (28/01/2015) :- You can install the “Anti-Ban” version of WhatsApp+ Plus from here (http://bit.ly/1awwivp), They have made the cracked version of WhatsApp+ Plus which can bypass the banning system of WhatsApp.
Update (31/01/2015) :- If you already got banned from WhatsApp then use this guide (Hacking-Guide Forum) : http://bit.ly/1Ew00xp