There is nothing ironic in the fact that people cannot afford to test their websites on every single device Apple releases. FYI, I just opened that website on my iPhone and it works great. Perhaps, the viewport meta tag was added here with iPhone in mind, before iPad was released.

Edit: indeed, this is a bug: there are different CSS styles for devices with < 480px screen width and > 480px (via @media CSS rules). Desktop browsers pick the latter style and ignore "viewport" meta tag. iPhone picks the former style and takes into account viewport. iPad picks the desktop style and takes into account viewport, which disables zoom (intended for the iPhone style version).

Now that I debugged the problem, can we instead report bugs to website designers instead of commenting here on HN?