First, you need a font that contains those characters. According to support information at Fileformat.info, the only font that has them is Symbola, though it is possible that some less known fonts have them too. Symbola can be downloaded from http://www.fonts2u.com/search.html?q=symbola or http://users.teilar.gr/~g1951d/ (the latter is for the author’s site, hence preferable when it works).

Second, browsers have difficulties with special fonts. They are often unable to pick up special characters from various fonts. I’m afraid that if a page does not explicitly mention Symbola (as it really should in cases like this), the only thing you can do as a user is to make your browser use Symbola as the default font, at least temporarily (via the browser’s general settings).