Celebrating Meelaad is a Bid`ah. Do not be fooled by people who speak to you about "Bid`ah Hasanah" (good Bid`ah). Shaykh Ahmad Sirhindi رحمة الله عليه used to say that every Bid`ah is Bid`ah Sayyi'ah (an evil Bid`ah).
Did Rasoolullaah صلى الله عليه وسلم celebrate Mowlood/Meelaad? No.
Did the Sahaabah celebrate Mowlood? No.
Did the Taabi`een celebrate Mowlood? No.
Did the Atbaa`-ut-Taabi`een celebrate Mowlood? No.
So who celebrated Mowlood? Shaykh `Ali Mahfoozh mentions that the ones who invented Moulood were none other than the Shi`as of the Faatimid Dynasty in Egypt and Morocco. The practice was later brought into Iraq by the King of Irbil, Muzaffar-ud-Deen ibn Zayn-ud-Deen `Ali al-Buktuki, a man who the historians say was a Faasiq who used to waste money. Moulood has never been the practice of the Sulahaa. In India, Moulood parties are incomplete without the singing of the dagga-smoking Qawwalis. The Moulood contains a number of evils depending on where it takes place in the world. In some places, there is even dancing of men and women. In others, there is music and singing. In others, the entire day is spent in festivities and Salaah is missed out. There is no goodness in Moulood. It is a Bid`ah which the Sahaabah would have fought against had they been here right now. They would have physically fought against the people who organise these Moulood parties.
It is a Baatil celebration by people who want to imitate the Christians. Like the Christians have Christmas, these Moslems want to have an "Islamic Christmas", and call it "Moulood".
Do not be fooled by the highway robbers who try to snatch away the Imaan of people.
Follow Islaam the way Sahaabah followed it. Read about the lives of the Sahaabah. Follow their Islaam. Don't follow the modernist, watered down joke people today have invented - like Suhaib Webb, "Yes-Sir" Qadhi, "Imaam of the White House" Hamza Yusuf, Tahir al-Padre al-Christian al-Jew al-Hindu al-Mushrik, etc. - and named "Izlam". "Mozlems". Be a "Muslim", not a "Mozlem".