If you, like me, have tried to install a Safari 5 extension such as Coda Notes, and were met with the following dialog:
and then spent 5 minutes looking through Safari’s Preferences window to no avail, this is how you enable Extensions on Safari 5:
1. Open **Preferences**
1. Click **Advanced**
1. Click **Show develop in menu bar**
1. Close and reopen Safari
1. Click the **Develop** menu item
1. Finally, click **Enable Extensions**
Viola.