Firefox (or Mozilla 1.7) will crash most of the time when you click 'Collapse', below. (Try again after a refresh if it doesn't crash the first time). The problem can be avoided by adding a single space between the <BR> and the <applet...> tag in FirefoxCrash.js -- no crash. Also, there's no crash if you remove the <BR>.
IE6 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.