Back up all data if you haven’t already done so. Before proceeding, you must be sure you can restore your system to the state it’s in now.
Quit Safari if it’s running.
Step 1
Select /Applications/Safari in the Finder and open the Info window. There’s a checkbox in that window labeled Open in 32-bit mode. If that box is checked, uncheck it. Close the window.
Hold down the option key and select Go ▹ Library from the Finder menu bar (Lion) or open the Library subfolder of your home folder (pre-Lion). Delete the following items from the Library folder (some may not exist):
Caches/com.apple.Safari
Caches/Metadata/Safari
Saved Application State/com.apple.Safari.savedState
Leave the Finder window open. Try Safari again.
Step 2
If it still doesn’t work right, quit, go back to the Finder, and move the following file from the open Library folder to the Desktop:
Safari/Bookmarks.plist
Then delete the following items (some may not exist):
Cookies/Cookies.binarycookies
Cookies/Cookies.plist
Preferences/com.apple.Safari.LSSharedFileList.plist
Preferences/com.apple.Safari.plist
Preferences/com.apple.Safari.RSS.plist
PubSub/Database
Safari
(Note: you are not deleting the Safari application. You’re deleting a folder named “Safari.”)
Try again. This time Safari should perform normally, but your settings will be lost. Select File ▹ Import Bookmarks from the Safari menu bar. Import from the bookmarks file you moved to the Desktop. Recreate the rest of your Safari settings. You can then delete the old bookmarks file.
Note: This step will remove your Safari Extensions, if any, and their settings. If you choose to restore them, do so one at a time, testing after each to make sure you haven’t restored the problem.
If you don’t like the results of step 2, you can undo it completely by quitting Safari and restoring the items you deleted in that step from your backup, overwriting any that were created in their place. You don’t need to restore the files you deleted in step 1.