Downgrade from Safari 5.0 to Safari 4.0.5
As a last resort to crashing and performance issues with Safari 5.0, you can downgrade to Safari 4.0.5. Unfortunately, although Apple maintains a Safari 4.0.5 download page, the Safari 4.0.5 installer will not run once Safari 5.0 is installed, stating that an older version of Safari cannot be installed over a new one.
To get around this problem, youll need to use one of the following options:
Archive and Install Mac OS X Use your Mac OS X installation disc to perform an archive and install process. Install all available updates except for Safari 5.0. Instead, download Safari 4.0.5 if that version is not installed by your Mac OS X disc.
First download and install Pacifist and the Safari 4.0.5 installer. Drag the Safari 4.0.5 installer package onto the Pacifist application icon to open it.
Once the Safari 4.0.5 package is open in Pacifist, select it from the list, then click Install in the upper left corner of the Pacifist window. Leave the use administrator privileges box checked.
Youll be presented with a dialog box that states Application already exists. Check Dont ask again for this installation then click Replace.
After performing this process, restart your Mac. Youll be left with an earlier version of Safari.