An occupational hazard, I currently have 11 different web browsers and most have number of debugging facilities turned on. I usually don't promptly turn them off when I'm done coding.
That has caused the "Do you wish to Debug?" alert on IE, for example, to become a close friend. The mind boggles at how many of the popular sites have script errors, which furthers the AJAX as infrastructure point.
Even this blog won't load without the innocuous invitation.