The Sunnahs of Jumuah
Are the Sunnah before or after Jumuah proven? There is indirect evidence for the four before but for the four or two after there is strong direct evidence. So taking the strongest first:
Some (not all) ahadith for Four rakahs after Jumuah:
Abu Hurayra reported that the Prophet (saw) said, “Whenever one of you prays Jumuah he should pray four rak’ahs after it.” (muslim)
Some narrations say he prayed two rakahs; Ibn ‘Umar reported that the Prophet (saw) did not pray after Jumuah until after he had gone back and would pray two rakahs in his house. (Muslim)
So 2 or 4 after Jumuah are directly proven so shouldn’t be missed.
Some ahadith indirectly proving 4 before Jumuah:
The Prophet (saw) would always pray 4 rakahs after zawaal (when the sun begins to set); some see these as being the 4 rakahs before Zuhr and that is not a problem for the 2 rakahs of Jumuah and 2 khutbahs replace the 4 Fard of Zuhr on a Friday. But nothing replaces the sunnahs so they should be offered as normal.
Abdullah ibn as-Sa’ib reported that the Prophet (saw) used to pray four rak’ahs when the sun began to descend before the Zuhr prayer. He said, ‘It is a time when the gates of heaven are opened and I want a righteous action to ascend for me in it.’” [Tirmidhi]
‘A’isha reported that the Prophet (saw) did not miss the four rak’ahs before Zuhr.” (Bukhaari)
Reading four rakahs sunnahs before Zuhr everyday is a very praised act. On Friday these would have to be before the Jumuah prayer:
Aisha reported that the Prophet (saw) said ‘Whoever prayed 12 rakah sunnah every day Allah will build for him a house in Jannah; 4 rakahs before Zuhr and 2 after; 2 after maghrib; 2 after Isha and two before Fajar.’ (Tirmidhi; Abu Dawud; Nisai & Ibn Majah)