If you remove the space between the <BR> and the <applet...> tags in FirefoxNoCrash.js, Firefox 1.02 (or Mozilla 1.7) will crash most of the time when you click 'Collapse', below. IE has no trouble with either variant.
The original problem showed up in this more functional Web page -- try expanding, then collapsing, the applet for any of the Life patterns. I was using document.all() instead of document.getElementById() at that point... but it doesn't appear to make any difference; Firefox 1.02 and Mozilla 1.7 crash with either syntax.