Yes, artistic standards. The source should look pretty. Although authoring HTML and CSS is a decidedly left-brained, analytic activity, the right brain's capacity for gestalt can play a valuable role.RealityTopia
This article at RealityTopia Blog gets into the inner workings of a template. George Mikos wrote his own template source out of a need for an easily customizable Blogger template. He not only shows you the how, he explains why. I am able to learn much easier if I know the reason behind doing something, and he certainly provides that. The article is easy to read and interesting. Much like his template source which he takes great pride in. And he should.
I fully intend to study his methods more. I am interested in it all, but especially in the use of the CSS float property to dynamically access the entire width of a computer display screen, be it 1024 x 768 or 800 x 600.
There is much to digest in his post. I highly recommend looking it over if you have any interest in building your own template.