What are the prayers that the laity can not read and why.
We commit the sin of sacrilege, because we assume the honour that does not belong to us. In this regard, Archimandrite Gregory offers a very instructive case: "A young man (he lives in Timashevsk), once visiting the Holy Trinity-St. Sergius Lavra, went to the bookstore and bought a book called "Service Book" (this happened in the early nineties). Service Book is a book that includes liturgical orders of service, containing sacramental prayers read purely by a priest. This fellow certainly did not know that a layman can’t read such prayers… At home he began to read this book including the prayers which only a priest befits to say. A short time afterwards the young man noticed some “warmth” in the body and felt “Divine grace”. The demon tempted him into a trap of delusion through the sensual deception. I warned this fellow that if he continued to engage in inappropriate things, then something bad could happen... But this young man ignored my admonitions, persuading me that Divine grace and Holy Ghost descended upon him… Soon after our conversation, at the moment when he was reading the priestly prayers again, a demon entered him ... Only his mother can tell us how much suffering and misery had he brought to himself and to his mother...
Here's an example that not all prayers can be read by a layman ... "
http://azbyka.ru/tserkov/duhovnaya_zhizn/molitva/5g11_9n-all.shtml (in Russian)