We would dearly like to say, "Yes, it is". Unfortunately, in the world of HTML coding not everything is that simple. The formulae on the site are marked up using MathML, the standard language for doing so. Unfortunately, Internet Explorer (from Microsoft) has chosen to not play ball entirely fairly with industry standards of coding. As a result, there are some fundamental, problems with the rendering of the site on IE (all versions).
Instead, we recommend (in order):
Google Chrome [3]
and have not yet encountered any problems browsing the site with the new version of Microsoft Edge. [4]