Know your (event) sources
Today, Peter-Paul Koch: addEvent Considered Harmful. And he's right, you can get into all kinds of headaches using IE's
attachEvent method, as my own
addEvent snippet does. Be sure to read the ensuing comment thread for some interesting alternative approaches.
Caveat implementor, my friends.
PS: I'm rather pleased that something I wrote merits a "considered harmful" treatise! I'm in good company.