Как вариант использовать такое...
<!DOCTYPE html>
<html>
<head>
<!--
<script src="http://code.jquery.com/jquery-latest.js"></script>
<link rel="stylesheet" type="text/css" href="tmp.css" />
-->
<style type="text/css">
</style>
<script type="text/javascript">
var new_nums=0;
var old_nums=0;
function startCounter(){
check();
timerID = setTimeout(startCounter, 10);
};
function redraw(){
ex = new String();
for(i=1;i<=new_nums;i++){ex+=i+"<br>";}
document.getElementById("holder").innerHTML=ex;
};
function check(){
var s=document.getElementById('iLines').value;
ar=s.match(/\n/g);
new_nums=(ar)? ar.length: 1;
if (new_nums != old_nums){
old_nums=new_nums;
redraw();
} else {
document.getElementById("holder").scrollTop=document.getElementById("iLines").scrollTop;
}
};
</script>
</head>
<body>
<table border=0>
<tr>
<td valign='top' width=30>
<div id='holder' style='height:400px;overflow:hidden;font-family:Courier New;font-size:11px;line-height:16px;padding-top:3px'>1</div>
</td>
<td>
<textarea id='iLines' name='text' style='overflow:auto;height:400px;width:95%;' wrap='OFF'>111</textarea>
</td>
</tr>
</table>
<button onclick='check()'>Go</button>
<script language='JavaScript'>
startCounter();
</script>
</body>
</html>
Но в этом варианте "не видно" последнюю строчку...
