Not, as you would think, private hire transportation for spiders, but a sniglet first used in 1998 by Steve Gruenwald to describe a taxonomy used to guide users to a website.
The term itself stems from Arachne, the weaver who according to Greek legend was turned into a spider, and taxis, a Greek word for a systematic arrangement of items, especially when using some form of classification.
Information taken from www.whatis.com - Word of the Day