We recommend using Firefox if you want to use the Client Side Editor on a Mac as the Java applet should work in Firefox without any additional configuration changes.
In order to run use the Client Side Editor in Safari, you need to make a change to Safari's security settings. This avoids a "Cannot run program "/usr/bin/open": error=1, Operation not permitted" error.
Go to Safari -> Preferences... -> Security.
Click 'Manage Website Settings...' next to 'Internet plug-ins'.
Next to the Asset Bank domain name, choose 'Run in Unsafe Mode'.
Unfortunately Java is not supported in Chrome on Mac OS X any more so it is not possible to use the Client Side Editor in Chrome on a Mac (see Java/Chrome FAQs ).