Sites such as http://www.nih.gov are largely controlled by mainstream medicine/Big Pharma and have been found to be biased and unreliable. The government itself has admitted a link between mercury and autism based on incidence of autism near mercury emitting plants and has also as much as admitted a link in their decision to award damages in the girl who had autism.
I am not arguing that there is no genetic link - obviously there is also a genetic link, but that genetic link appears to be a very common one, perhaps as common as 1 in 50 to 1 in 150, and mercury clearly is a causal agent in the presence of that link. Therefore, in at least 1 in 50 to 1 in 150 children, mercury could cause autism. Mercury and other toxins may even play a role in the development of the genetic link.