Joe Gregorio's announcement about a new version of sparklines reminded me that I wanted to look at this more closely. I love projects of this type: small, and useful. Here's the beauty of the thing: given a comma separated list of values, you can generate an image of a graph, in a number of representations. How's that for a problem statement and solution, in one sentence? Even better, Joe's handling conditional GET in a really simple way: write the current program version to the ETag; since the output of the program is deterministic, the decision to return 403 is simply the determination of whether the program version's changed.