When you open an email with an attachment there will be automatically displayed preview. Through the Preferences menu of the Mail application there is no option to turn this feature off. You can disable the preview with the following command:
Month: March 2013
Activate OS X Finder in Simple mode
The ‘Simple Finder mode’ hides desktop files, and won’t let anyone open a new Finder window. Only applications in the Dock can be launched. Note that Spotlight can still be used for launching items. This command could be a nice alternative for setting up restrictions without a guest user account. Click Finder ▸ Run Full Finder, and then type in your admin password to start Finder in normal mode.