What you have come upon is an experiment in scholarly writing. In one sense, it is a traditional artifact: introduction, text, commentary. But the hypertext medium encourages one to put the text at the center of the exercise and to make scholarly writing once more, as it was in the middle ages, marginal. Further, hyperlinks embedded in the text refer beyond the nominal boundaries of this exercise to other WWW resources, mainly items prepared for other purposes by the author. (The background color of these pages is consistent, and thus a shift in hue will warn you that you have ventured into different territory.)
In such an environment, text and hypertext begin to exchange places, and it is possible to have notes on notes, etc. Whenever you are in doubt, hit "back" a few times and you should return to the last place where you were unconfused.
This is frankly an experiment: comments, questions, suggestions to J.J. O'Donnell
If you wish to skip the foofaraw and explanation and begin with the text, you do so with my great encouragement and blessing! The alternate paths are to read through the introduction with care and then go on to the text, or to begin with the translation and then go on to introduction or text.