Links in popup point to incorrect URL/domain

check in your footer, bottom right, you also get this
"Site by DVisions"
>> it also has the link, I don't know what it is but this is the cause. May be the company that created the website ?

Yes it is, but I can't see any reason that your buttons would inherit that URL link. There must be a script somewhere picking it up from somewhere to add it to the button. I think you're probably right that it's a script / plugin doing it, so I'm going to have a play and see what I can find...