OK, I've had a Mac for 8 years and this is the first time so I really don't know what software ro what one can do to fix it.
I cannot use Safari ro Google Chrome because I get bombarded with multiple tabs opening all sortso of things like MacKeeper, Win a free Apple iPhone, Surve Junkie and even automatic downloads of multiple times of MacKeeper (never installed MacKepper) but have seen adverts on webpages for it. The only website I don't have issues with is eBay, but any other site I can only use Firefox. I tried logging into this site via Safari and tried Google Chrome and ended up with about 10 tabs of ads and junk and couldn't log in.
Is there anyway to fix this or is it just better to reinstall the OS and then painfully reinstall everything?