I'm not sure if this belong in this section, so I would appreciate if mods put it in the proper place if they feel that it should be in another sub-forum.
This is a topic that Islam has been criticized for unfairly, and it is obligatory to clear up this confusion since it keeps coming up. The prohibition of mutah also known as temporary marriages occurred in the time of the Prophet peace be upon him, but it still practiced today by Shias. See this article on mutah
for complete evidences.