Thanks!
Here's a reference on it from http://www.maaref-foundation.com/english/shia_education/shia/12.htm :
One of the most misunderstood aspects of Shi'ism is the practice of dissimulation or taqiyah. With the. wider meaning of taqiyah. "to avoid or shun any kind of danger," we are not concerned here. Rather, our aim is to discuss that kind of taqiyah in which a man hides his religion or certain of his religious practices in situations that would cause definite or probable danger as a result of the actions of those who are opposed to his religion or particular religious practices.Many here have been asking themselves "How could Muslims possibly believe the obvious falsehoods that are coming out of their mouths". Quick answer: they don't. It is part of Islamic doctrine that, when faced with a situation where telling the truth would work against Islam or fellow Muslims, YOU LIE. You tell whatever story seems most likely to work to your advantageAmong followers of the different schools of Islam, Shi'ites are well known for their practice of taqiyah. In case of danger they dissimulate their religion and hide their particular religious and ritual practices from their opponents.