Lots of rethinking being done as I try to cast the text of the presentation into graphical format; I've ended up regenerating a bunch of the graphs to include two types of data on the same graph, for clarity and efficiency.

Also, while formatting the presentation, we learned that to make centring of an XHTML block element work reliably through CSS, you not only have to use margin-left: auto; margin-right: auto; you often also have to include left: 0; right: 0; (or some fixed values). This is necessary when the element is position: absolute.