With the release of OS X 10.8 (Mountain Lion), Apple introduced a new security feature called Gatekeeper, which helps you to keep your computer free of malicious software. Gatekeeper allows only software from trusted sources to be installed: Applications from the Mac App Store, and applications from registered software vendors who have built their installers with a Gatekeeper signature. As QuarkXPress 9.3 was released before Apple introduced this new feature, Gatekeeper (at its default settings) does not allow the installer for QuarkXPress 9.3 (or earlier) to launch.

However, there are two ways to install QuarkXPress 9.3 (or earlier) under Mountain Lion:

· Control + Click the installer icon and choose Open.

· Open System Preferences, click Security and Privacy, display the General tab, and then click Anywhere under Allow applications downloaded from. (After installation, be sure to return this setting to its default state.)

In a few weeks time, Quark will release a free update for QuarkXPress 9 that is compatible with Gatekeeper and has been extensively tested on Mountain Lion. That version of QuarkXPress will be the first official version supported on Mountain Lion. Until this upcoming version is released, Quark recommends that you use QuarkXPress 9.3 on Mac OS X Leopard, Snow Leopard, or Lion.