Just now I was on the page http://www.usenix.org/event/hotbots07/tech/full_papers/provos/provos.pdf trying to reproduce a bug in WebKit-SVN-r30354.dmg.

I got the following pop-up:
------
Acrobat is attempting to connect to 
http://www.invisionboard.com

If you trust the site, choose Allow. If you do not trust the site, choose Block.
------
I wish I knew who produced that warning.
Ironically I think that URL appears only in a sample of html whose purpose is to illustrate a browser vulnerability.
The site www.invisionboard.com was presumably an innocent victim.
It resides in the pdf files as text—not a link!

I had just reported a bug via the bug button. The reported bug had messed up the pixels and so I tried command R. It crashed.

Below is the text in the bug report resulting in the crash.
-----
To reproduce original bug: browse http://www.usenix.org/event/hotbots07/tech/full_papers/provos/provos.pdf
Magnify text by small blue plus button to 300%.
All scrolling below is two finger mode.
Scroll down to page 3 where there is some text that extends a bit into the right page margin.
Shrink the browser window in both height and width.
Any horizontal or vertical scrolling acts now only on a subset of the pixels.

Switching focus away from Safari fixes pixels but only until further scrolling.