Is it possible to recite prayers for the dead?

O Allah, Instill Happiness in the Spirits of the Inhabitants 
of the Grave.Imam Jaffer As-Sadiq (as) was asked:

“Is it possible to recite prayers for the dead?”

He replied, “Yes,” and added: “Surely a dead person rejoices when he is pitied and forgiveness is sought for him, just as a living person rejoices upon receiving a gift.” (al Mahajjatul al Bayda v. 8, p.292)

The Holy Prophet (pbuh) once passed by the grave of a person who was buried a day before and saw his family weeping.  Observing this, he said: “Indeed, two small units of prayer which you consider insignificant is more lovable to the inhabitant of this grave than your world in its entirety.” (Tanbihul Khawatir, p.453).

Imam Jaffer As-Sadiq (as) has said “Prayers, Fasting, Hajj, Sadaqa, good deeds and Dua reach the dead in his grave, and their reward is written for [both] the doer and the deceased.” (Wasailal Shia, Tahsili Masail a Shaaria, v. 8 p.279)

These ahadith clearly indicate the importance of remembering and praying for the dead.  No wonder one of the most important and recommended duas to be recited in the Holy month of Ramadhan begins by remembering the deceased!

(ref.Manifestations of the All-Merciful, by Abu Muhammad Zaynul Abidin)