Probably via Terminal like many other things in OS X.
http://www.macosxtips.co.uk/index_files/12-tips-for-safari-4-beta.html
Hopefully this debug stuff still works in final.
Thanks, I tried a couple of those and they don't seem to have any effect. I wonder if Apple removed the commands completely, or if they just changed the name of commands for the final release. Is there some site that might have updated info on these terminal commands?
EDIT: reading through the comments on the page you linked to shows that other people are reporting the same thing, that these commands do not work on the official release version of safari 4.