AdBlock with cat paw, advertisments now become cats. Malware Problem?

I have AdBlock extension installed. It’s been installed for about 3 weeks or so. Now, whenever an advertisement on a page is blocked, it is replaced with a picture of a cat, and the icon for AdBlock in the toolbar shows a paw print instead of a hand palm in “halt” position. Is this normal behaviour, or could this be a sign of a security or protection problem?

Also, when hovering the mouse on one of the cat pictures, there is a “Learn More” hyperlink. when I click on it, Comodo Dragon shows a page, SSL warning, “It may not be safe to exchange information with this site.”

Do I have anything to worry about? I find no other troubling behavior. (and I do not yet continue onto the site beyond the SSL warning).