Did you know that that was a slideshow? You're seeing the title page, click on it to advance to the next page. repeat.
Arrow keys also work.
That said, this is pretty poorly designed. I also had no clue what to do for the first few seconds after I clicked the link. It was only at slide 38/41 that I noticed the tiny, hidden controls on the very bottom blending into my status bar.
I didn't even notice those. Fortunately, I've worked with systems like S5 slideshows, and this looked a lot like a slideshow (no scroll bar, large text, numeric fragment in the URL).
Usability could definitely be better, but I will admit to writing up similarly boring slides in the past.
I wonder why 280slides never really took off. This still seems like an unsolved problem (hosting slides online)
Slideshare and Scribd: both allow you to use the program you already know (Keynote or PowerPoint, most likely) that's also a native app with lots of powerful functionality.
I don't know if it's Opera being smart, but space works for me as well.
And on an iPad, nothing works.
Except that, depending on your browser, it is impossible to navigate to the second slide. In opera mini, the slide itself is not clickable, there are no arrows visible, arrow keys are not available, and the "contents?" link points to a trunkated list starting at slide 15. I'd really like to read the presentation, but it is completely inaccessible.