Safari and Facebook problems

Hi,

I have had repeated problems with Facebook and Safari over the last few months.

I usually get redirected to a site lundblah or something when I try log onto facebook.

Occaisionally it happens in the middle of surfing facebook, other times it happens when I first direct my browser there.

The address bar still says facebook.com however the page loaded is definately NOT.

Another more recent problem is I get a access denied message, or something similar.

I was told awhile back to change my dns settings to open DNS and following a post on these forums I did this.

The problem still happens. I know people say there is no such thing as a Mac virus but I am convinced something is not right.

Heres a screenshot of the latest problem. Its the same regardless if I google search 'facebook login' and click the link or just type Facebook.com into my browser.

I am on a 13' Macbook Pro, running 10.8.8 and Safari.

Can someone please help me clear this up?

Ontop of this my browsing speed has been very slow recently and I am not sure if this is related.

Thanks in advance.