Question: Is there a sunnah prayer before Jumu^ah or not?
Answer: Yes, 4 rakaah in one sunnah prayer. It is made after the Athaan that is made once the Thuhr time has entered, but before the Khutbah. If the sermon starts immediately, then you can make it up after prayer.
Ibn Mas3uud used to order his followers to pray 4 raka^aat before Jumu^ah. Zain al-Deen Al-^Iraaqi mentions in his book Tarh-Al-Tathriib that the weak hadith of Ibn Maajah, which explicitly says to pray 4 rak^ah before jumu^ah, has been related through an acceptable chain by al-Khula^iy in his "fawaa'id".
... and Allah knows best.