Unable to open Preferences in Safari.

The keyboard shortcut show the keys you need to use (Command and comma keys) or you can also click on the Preferences... menu option.

Safari preferences may be corrupted after upgrading to Yosemite. It can happen.

Quit Safari if it's open.

Now open a Finder window. From the Finder menu bar click Go > Go to Folder

Type or copy paste the following

~/Library/Preferences/com.apple.Safari.plist

Click Go then move the com.apple.Safari.plist file to the Trash.

Relaunch Safari to test.

Make sure your Mac is running Yosemite becasue your Safari > Preferences drop down menu is from Mavericks, not Yosemite.

Click your Apple menu  top left in your screen.

From the drop down menu click: About This Mac

Which version do you see?

Ok... v10.10.3... that's Yosemite but it needs upgrading to v10.10. 4 and Safari to 8.0.6

Open your App Store then select Updates from the menu top of the App Store window.

Install the available updates then restart your Mac then try Safari > Preferences.

Delete the cache.

Open a Finder window. From the Finder menu bar click Go > Go to Folder

Type or copy paste the following

~/Library/Caches/com.apple.Safari/Cache.db

Click Go then move the Cache.db file to the Trash.

Quit and relaunch Safari to test.

Now that you have updated Safari, try the .plist file one more time.

Quit Safari if it's open.

Now open a Finder window. From the Finder menu bar click Go > Go to Folder

Type or copy paste the following

~/Library/Preferences/com.apple.Safari.plist

Click Go then move the com.apple.Safari.plist file to the Trash.

Relaunch Safari to test.

Please read this whole message before doing anything.

This procedure is a test, not a solution. Don’t be disappointed when you find that nothing has changed after you complete it.

Step 1

The purpose of this step is to determine whether the problem is localized to your user account.

Enable guest logins* and log in as Guest. Don't use the Safari-only “Guest User” login created by “Find My Mac.”

While logged in as Guest, you won’t have access to any of your documents or settings. Applications will behave as if you were running them for the first time. Don’t be alarmed by this behavior; it’s normal. If you need any passwords or other personal data in order to complete the test, memorize, print, or write them down before you begin.

Test while logged in as Guest. Same problem?

After testing, log out of the guest account and, in your own account, disable it if you wish. Any files you created in the guest account will be deleted automatically when you log out of it.

*Note: If you’ve activated “Find My Mac” or FileVault, then you can’t enable the Guest account. The “Guest User” login created by “Find My Mac” is not the same. Create a new account in which to test, and delete it, including its home folder, after testing.

Step 2

The purpose of this step is to determine whether the problem is caused by third-party system modifications that load automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Please take this step regardless of the results of Step 1.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of Steps 1 and 2.

Can I just delete Safari and reinstall it?

No. You can reinstall OS X, but that's usually not the solution to any problem.