This update contains improvements to stability, accessibility and security, including the following:

More accurate Top Hit results in the Address Field
More accurate timing for CSS animations
Better stability when scrolling through MobileMe Mail
Fixes an issue that prevented Google Wave and other websites using JavaScript encryption libraries from working correctly on 32-bit systems
Fixes an issue that prevented Safari from launching on systems with network home directories
Fixes an issue that could cause borders on YouTube thumbnails to disappear when hovering over the thumbnail image
Fixes an issue that could cause Flash content to overlap with other content on www.facebook.com, www.crateandbarrel.com, and other sites when using Flash 10.1
Fixes an issue that prevented boarding passes from www.aa.com from printing correctly
Fixes an issue that could cause DNS prefetching requests to overburden certain routers
Fixes an issue that could cause VoiceOver to misidentify elements of webpages
For detailed information on the security content of this update, please visit this site: About Apple Security Updates.

SHA1 Safari Tiger = 6aec6f1a1738a7df43a8e339b875dd48ed7997d3

For explanation of what a SHA1 digest is, please visit this website: About SHA1 digest