Scroll to bottom of textarea

ok so i have a textarea which is constantly being added to from a text file with the php include command. that textarea is in one .php file which is also being constantly refreshed every 20 seconds. another page on the site is showing this textarea with an iframe (no scroll). what i want is that after each refresh the scroller in the textarea automatically goes to the bottom of the textarea.

ive tried to search this but nothing seems to work i also tried to use this

textareaname.scrollTop = textareaname.scrollHeight;

but im not sure how that fits into my page and if it even works

also i found this

<textarea id=“ta”>___</textarea>
<script type=“text/javascript”>
function f(ta_id){
var d=document, ta, rng;
if(ta && ta.createTextRange){

but it only works in ie


also the textarea is not in a form and has no buttons

This resource should be of some help then - Introduction to Range