The progress bar in the animation within graybox does not work if you do the following:

1) Begin loading a page with an applet
2) Click on the browser back button before the loading is done
3) Now go back to the page with the applet by either clicking on the link to that page or by using the browser forward button.

Notice the progress bar has now stop, but the applet continues to load until done.

See example:

http://javaweb.sfbay/~sc33349/projects/phonehome/applethtml/GrayBoxTest-09.html