Rambler was a Russian-language search engine (as well as portal and directory) back when Yandex hadn’t yet steamrollered everybody else and Google, being incapable of understanding nouns can have more than a couple of forms, was a non-starter. They were irrelevant by 2010 and gave up on mantaining their own index even earlier, I think.

Rambler TOP 100, then, is a website popularity rating from back when voluntarily placing such things on your pages using was cool and you showed them off using these buttons. I don’t think I’ve ever seen it on an English-language page (that wasn’t an obvious translation) before. Apparently it still survives in some form, though I’ve no idea who is in charge of it now.

That is to say, I have no idea why anyone would include that on their pages in this day and age, yet it is hardly nefarious. (Not that you’re supposed to know that, but if you publicly claim it is people will naturally expect you to have done some research beforehand.)