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;
}