Status Bar Display

Hi There I am in the process of learning how to build web pages and have been going through a program called professor teaches HTML I have just got to a section which introduces java script it shows you the way to include a message in the status bar and not the url when you hover over a link. This seems to work fine in IE but in Opera it still shows the URL and in Mozilla and Netscape it just has the word Done in the status bar. Is there a way round this or does some browsers just not support this item. I have included one line of the code that works in IE. Your comments would be much appreciated.

<a href="About Us/About Us.html" onMouseOver="window.status='This is All About Us';return true"
onMouseOut="window.status='';return true"><li>About Us</li></a>

Kindest Regards Tony B.