Pfui - 3:03 pm on Sep 28, 2011 (gmt 0)
Unfortunately, Slurp/3.0 apparently retrieved countless pages before I realized it was scraping graphics.
Thus now, every single time it re-visits, it generates 403s galore for all the files it's now denied -- files it was trusted not to 'take' in the first place.
For example, this visit netted 1 html -- and racked up 39 errors (in a curiously slow 16 seconds):
Mozilla/5.0 (compatible; Yahoo! Slurp/3.0; http://help.yahoo.com/help/us/ysearch/slurp)