This is Information from Software Update.For Safari users, please take note some improvement.SO for those who already fed-up with their web browser, you might want to try out Safari new version 4.0.5.
This update is recommended for all Safari users and includes improvements to performance, stability, and security including:
Performance improvements for Top Sites
Stability improvements for 3rd-party plug-ins
Stability improvements for websites with online forms and Scalable Vector Graphics
Fixes an issue that prevented Safari from changing settings on some Linksys routers
Fixes an issue that prevented some iWork.com users from commenting on documents
For detailed information on the security content of this update,visit http://support.apple.com/kb/HT1222.