Upcoming Java 7 update 51, scheduled for January 2014, will prevent unsigned applets from loading at default security level. This means NetDiagram 4.* and older versions will stop working in applet mode since they come with unsigned applets. If anyone needs to keep using older versions in JavaApplet mode, you can do that by signing JDiagram.jar with your own digital certificate.

With missing support for applets on mobile devices, Chrome and Firefox browsers showing applets as a security threat by default, and Oracle changing applets security model every three months, Java usefulness as web front-end technology seems to be coming to an end. We plan to change default ClientSideMode value to Canvas for next release, with the drawback that it will not work on IE7 and IE8, which currently have about 11% market share (sources Global Web Stats and StatCounter). If anyone uses a show-stopper feature in JavaApplet mode that's still missing from Canvas mode and preventing you from moving to latter, let us know and we'll adjust our release roadmap accordingly.