Actually this is a report on a problem solved. When I upgraded Safari to v3, I started getting a blank page when I tried to view the page source. Turns out that long ago I had installed a neat little utility called SafariSource that applies color-coding to the source HTML you see (like the color coding that's built-in to Firefox.) It installs as a SIMBL bundle in Library/Applications Support/SIMBL, and once it's there it appears to be part of the app, not turning up anywhere when you check plug-ins and such.
It just needed to be updated to a newer version to work with Safari 3.
In researching this problem, it's clear that Safari 3 doesn't play nice with a lot of plug-ins and add ons that worked with all previous versions. So, the answer to almost any buggy behavior with v3 is to start by disabling all these and updating where needed (once you remember you installed them in the first place

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