It occured to me a while ago that with the increasing number of planetplanet blog aggregators and similar things springing up, people who wish for their XHTML to be displayed in an aggregator are going to have to come to some kind of agreement about the meaning or style of certain things.
Take newsdot, for example. Recently I published an entry with some images in it. The images are wrapped up inside <div> tags, with a class of image. Cph recently published a transcript of a computer session, which he did as a <ul> tag with a style attribute.
In the former case, the <div> tags were preserved but bereft of their meaning without my stylesheet. In the latter, the style attribute was stripped out.
We should decide on a set of div/span classes and ids which mean certain things, to be sure what we write appears properly on the aggregator.