On Mac OS X, the site definitions are stored in the preferences. On OS X (as a multi-user OS) there is one Prefs file for the installation, and one for each user using Dreamweaver. Back up the file, which you can find at the following locations:
Dreamweaver 4 users:
users/<user>/Library/Preferences/Dreamweaver/Preferences
Dreamweaver MX users:
users/<user>/Library/Preferences/Dreamweaver MX Prefs
Dreamweaver 2004
users/<user>/Library/Preferences/Dreamweaver MX 2004 Prefs
Dreamweaver 8 users:
users/<user>/Library/Preferences/Dreamweaver 8 Prefs
To back up the file, make a back-up copy and store it on a safe place. Do not change, add, or remove anything in that file!
To restore your site definitions copy the Site prefs file back into the prefs folder.
Note: This will work only if you did not change anything like path to the sites, site names, etc.
Tip: Also on a Mac, the best and safest way to back up site definitions is to use Dreamweaver's export/import feature! In this way, Dreamweaver creates the STE, which you can import into Dreamweaver on other Macs and Windows too.
In this article, you learned how to back up your site definitions in Dreamweaver. For more information, check out the following resources: