I keep everything up to date via the Java control panel (currently 1.7xx soon to be 1.8) so was surprised to see this: Then I remembered that I had done some Java development in the past and installed various jdks from Oracle so I ran: I made sure that the Safari and Java preferences were set the same on each machine but still no joy. But on the third Mac, everything worked fine. On two of the Macs, as soon as I fired up the Citrix app, the Java vpn window would show 'error'. Once that was all done, I could log in from all my Macs, fire up the applet and establish a secure connection. The first thing is that you have to do some configuring of both Java and Safari to get the applet to run at all. The applet is a simple vpn client from Juniper that lets me access a Citrix Desktop from any Mac that I can install the Citrix receiver client on so I can work on 'Company stuff' from a large screen iMac when I'm sat at home or from my MacBook when I'm on the road (it works fine over 3/4G). Recently, I was trying to get a Java applet to run in the same way on 2 iMacs and my MacBook Air. I sometimes find the Java setup on my various Apple devices to be a mystery.