Sure, but the point is, to put together any decent web page template, you'll need at least:
1) Your server-side language (e.g. Ruby)
2) Your templating language (e.g. ERB, which may be very similar to 1)
3) HTML
4) CSS
5) Javascript
5 languages is pretty much a minimum unless you're doing something trivial. I'll agree that the onclick should be extracted, but as has been pointed out in other places, this is a quick documentation example, so it is reasonable to use onclick there to keep it brief.
PS: Also, perhaps worth pointing out that HTML and CSS aren't actually programming languages... Should they count? probably not.