check this thread : http://www.joomlart.com/forums/topic/something-is-broken-with-firefox/
Your code seems to be loading a different file and it seems to be : /t3-assets/jsa1395.js, which loads mootools 1.2.4
Check the other thread and add the lines :
String.prototype.contains = function(string, separator){
return (separator) ? (separator + this + separator).indexOf(separator + string + separator) > -1 : String(this).indexOf(string) > -1;
};
After
var MooTools={version:”1.2.4″,build:”0d9113241a90b9cd5643b926795852a2026710d4″};
See if that helped you.
Good luck.