This seems like it could be a post in itself. Firefox used to actively block me from sites. Don't remember what I did to get them to stop, but I still get warnings. Being ignorant as I am on it I've been wary of sites due to all the warnings. I still venture onto them as I don't plan on logging in or anything, but still not certain of the exact risks that make them so adamant they should be avoided at all costs.
RE: Vaccination is based on a false premise