This was handy for me & worked, I came across this handy site which can opt you out of many ad networks, it adds a cookie to make sure you dont receive targeted ads whilst in a webpage & helps to keep some form of privacy, I dont expect it to be some miracle cure to stop them seeing what you look at, but its a step in the right direction for some marketing spam companies to follow & certainly one I'd respect.
Network Advertising Initiative
Network Advertising Initiative