How to get rid of McAfee pop-up spam on Safari?

Hi all. first time I have had any unwanted intrusion whatsoever on my MacAir. Yesterday I clicked on a weblink and it went to a dodgy looking McAfee page. I closed immediately and have cleared cache and history and downloads. BUT all day today is popping up when I am in Safari browser this small box from McAfee, or a fake of it, saying I have viruses. I don't - it's spam. But how do I get rid of the bugger? It is annoying me.

Above link the dodgy page causing this.

Any advice welcome ;)))

Thanks

Deb

[Edited by Moderator]