if (typeof Array.prototype.indexOf === 'undefined') {

	/**
	* 15.4.4.14
	* NOTE the second parameter fromIndex is not explicitly stated so that the
	*      method's length property becomes 1
	*
	* @param searchElement array element to be searched for
	* @param fromIndex (optional, integer)
	*/
	Array.prototype.indexOf = function (f) {
		var l = this.length,
			i = arguments[1] || 0;

		i += (i < 0) ? l : 0;

		for (i = Math.max(i, 0); i < l; i += 1) {
			if (this[i] === f) {
				return i;
			}
		}
		return -1;
	};
}

…außerdem gefällt mir dieses Syntax-Highlighting hier :D
to be extended…