When the causes of autism are not known, there is no credible evidence supporting any cause. Are you suggesting genetics, or is the correlation between autism increase and mercury-laced vaccines something we can afford to wash our hands of. I am a father of a child born in 2000 who had mercury in his vaccines and he has been diagnosed with Asperger Syndrome, a high-functioning autism. I will investigate any and all possible causes, and certainly wont be dissuaded by someone who visits a couple web sites and ordains this a non-issue.
It does appear credible that genetics plays at least some role. As far as thimerosol is concerned, the correlation between mercury and autism appears to be spurious, insofar as places that eliminate thimerosol from vaccines do not observe a corresponding decline in autism diagnoses - another poster referred to a Danish study that showed this quite clearly, if you'd like to google it up.
Anyway, it's not that I don't want it to be mercury, or I have some vested interest in it not being mercury - I'd be quite satisfied if the evidence showed that thimerosol was a significant risk factor, since then we'd know what to do to improve the situation. Unfortunately, it seems that life is not that clean and neat in this particular case.