Important note: Safari (from version 12), Google Chrome and Mozilla Firefox (version 52 and later) have limited their compatibility with the technology required for Java Applets (NPAPI).Therefore, if you want to perform a procedure that requires Java, the browser you need to use on Mac is Mozilla Firefox before version 52.Also, please note that installing Java 8 on Mac requires an OS X version 10.7.3 or higher.
You can expand this information by visiting the Java website.
However, if you use a Safari 11 version to access procedures that still require Java and the Java plugin is not executed correctly, follow these instructions on how to set up in Safari:
Access the browser preferences panel by going to 'Safari', 'Preferences’ and select 'Websites’.In the "Modules” section, on the left, check that the Java module is enabled and select it to view the different websites you have visited and that use Java.
Next, check that the Tax Agency website and the "Local documents" website (required for Forms such as 340) are enabled and are not executed in safe mode.To do this, click on the site's drop-down menu with your mouse, while pressing the "Alt” key (Windows keyboard) or "Option" key (Mac keyboard) to display the options.You must select "Activated" and uncheck "Run in Safe Mode"
It is very important that you keep 'Option’ (Mac) or 'Alt’ (Windows) held down when you click on the drop-down menu, so that you see the option 'Execute in safe mode'.
Once this option is unchecked, a warning will appear in which you must press "Confirm" to confirm the deactivation of the safe mode.
An exclamation mark icon usually appears beside the dropdown if secure mode has already been disabled.This set up must be made for the Tax Agency websites as well as for the 'Local documents' websites.
Once you have checked if this was done properly, refresh the window to allow the applet to run properly and gain access.