I agree it would be great if there was a good HTML template the IEEE or ACM used. Even using Latex you spend ages making it look exactly the way you want and don't want to upload a dodgy HTML version.
The major difficulty, I think, are figures. How can we maintain keeping figures near the text that talks about them, and also allows a high density of them? The best I can come up with is a narrow column of text on the left (similar in size to a column of text in an ACM or IEEE double column format), and a larger column on the right with figures. The difficulty is in anchoring the figures in the right column with the text. But then you may have a bunch of figures piled up in one place, and a sensible layout becomes difficult to do.
I guess they just uploaded the final version they published in EuroSys 2011. Like all ACM conferences I know about, PDF is the way it is done. They would have to reformat for HTML.
