I installed a program call MacKeeper, when I found strange things happening with Safari web-browser I uninstalled it.
When using https://cnet.com or https://mail.com or a proxy server using http:// the MacKeeper advert was no longer there.
Does anyone know how this company managed to hack these adverts into webpages I view?
Here's the Apple discussion thread on solving the problem.
]MacKeeper can't be deleted