Annoying Security Alert message on every web page

Sorry if I'm in the wrong forum.. This is my first post.

 

I used McAfee until a month ago.. About the time I started with Norton, I started getting this message up in a window:-

 

Security Alert: Revocation information for the security certificate for this site is not available. Do you want to proceed?

 

This comes up on every web page I visit, up to 12 times for each page, even on the AOL opening page. It's driving me nuts! I was on to the AOL helpline and they told me it's probably from an expired security program. (McAfee?) I deleted all McAfee programs from my PC when I changed to Norton and Norton also did the same automatically. I'm waiting a reply from McAfee. Anyone any ideas please?