I assume everyone does this but I’ll blog it anyway. One of the best ways to find out the technology powering a well designed site is to generate an error condition.
Most sites litter clues as to their implementation all over the place, must to consternation of the Cool URIs school of thought, but its an interesting paradox that the sites that are the most interesting, and best implemented are the ones that are most silent about their underlying technology.
wget -S http://example.org can sometimes tell you a bit, but you really need an error message to uncover the deep dark secrets.
I was reminded of this quite by accident today, when I ran into an error on del.icio.us. The answer is Mason, which I must say raises my estimation of Mason considerably. Now if only it was open source.
update (2004/9/15): or flickr runs PHP and Smarty