I have an applet that works fine on all the Windows machines I have tested it on, in both IE and Firefox but does not load on Macs. They say they see a red X instead of the applet.
What are possible reasons for this? What can I try that might fix the problem? I am confused because I thought Java should run the same way no matter what the underlying operating system.
The only clue I have found so far is that the Macs seem to have Java 1.5 and Windows have Java 1.6. But I compiled it with version 1.5 (in eclipse: Run > Run Configurations > JRE> Execution Environment > J2SE 1.5 (Java)) and it still doesn't work on Macs.
You can see details about the problem in the "Java Console". If that isn't started automatically when the browser encounters an applet (it's a small window that may be behind the main browser window), then you need to enable it: Run /Application/Utilities/Java/Java Preferences.app, and check "Show Console" in the "Advanced" tab. If you now restart the browser, the Console should be shown if you run an applet. In it, there's much detail about what's happening with the applet, and most likely an error message of some kind.