It's up for debate. They have some evidence that part of the cause of Autism could be Mercury exposure from Vaccines and other places. However, they haven't scientifically proven much of anything.
I have a 4 year old, and I worry about that too, I have read about it, and I am still not sure, one side is so sure it does, and the other is so sure it doesn't. I get the thimerosal (mercury) free shots for him just in case.
This is untrue. Numerous studies have shown that vaccines have no relationship with autism. Moreover, the risk of a child suffering serious problems due to a disease caught because they are not vaccinated are much greater than getting autism.
Vaccines are quite dangerous for a number of reasons and should be used with extreme caution. For this reason, I do believe that it is possible--though not yet proven beyond doubt--that mercury in vaccines maybe be pratly to blame. More research may be needed. The USA has a special fund for those who have been injured by vaccines.