As helpful as stopbadware.org can be, the best defense against viruses is a layered defense, starting with good anti-virus and anti-spyware software on your computer. Google's software bundle includes a basic version of Norton, and there are other free anti-virus programs available online.
I think it is not possible. Why means in search for some websites it shows this site may harm your computer but there are many damaging sites which google doesn't recognise.