var isNN = (navigator.appName.indexOf("Netscape")!=-1);
function autoTab(input,len, e) {
	var keyCode = (isNN) ? e.which : e.keyCode; 
	var filter = (isNN) ? [0,8,9] : [0,8,9,16,17,18,37,38,39,40,46];
	if(input.value.length >= len && !containsElement(filter,keyCode)) {
		input.value = input.value.slice(0, len);
		input.form[(getIndex(input)+1) % input.form.length].focus();
	}

	function containsElement(arr, ele) {
	var found = false, index = 0;
	while(!found && index < arr.length)
		if(arr[index] == ele)
			found = true;
		else
			index++;
		return found;
	}

	function getIndex(input) {
	var index = -1, i = 0, found = false;
	while (i < input.form.length && index == -1)
		if (input.form[i] == input)index = i;
		else i++;
		return index;
	}

	return true;
}