Okay, now for the "official" answer...LOL. All Christians crossed themselves head, stomach (or breast), right then left until the medieval period. I no longer remember the pope of Rome who changed the rubrics for use with the Roman service. All Christians went from right to left, but when the priest blessed the laity, from the laity's perspective he did it from left to right due to the mirror effect. So the Pope reversed the rubric so that the hand motions of the priest matched the hand motions of the laity. Communications being what they were, the laity misunderstood and reversed the way they crossed themselves. The Anglicans have probably made a slight variance over time as well.. . The right to left has a symbolic meaning. Since this symbol goes with prayers of "Father, Son and Holy Spirit," it can be looked at as Jesus descending from the Father in Heaven, coming to Earth, ascending sits at the right hand of the Father, and sent his Spirit to dwell in our Hearts. Likewise, the Orthodox and Oriental Catholics will bring their first three fingers together for the three persons of the Trinity and keep the two final fingers together to remind of the divine and human nature of Christ.