You should never put crucial information in the status line. If many users might need the information, it should instead be displayed within the applet area. The status line is not usually very prominent, and it can be overwritten by other applets or by the browser. For these reasons, it's best used for incidental, transitory information. For example, an applet that loads several image files might display the name of the image file it's currently loading.
Applets display status lines with the showStatus method.