<textarea id="txt1" rows=10 cols=20>
</textarea>
<script >
if(navigator.userAgent.indexOf("MSIE")>0){
document.getElementById('txt1').attachEvent("onpropertychange",txChange);
}else if(navigator.userAgent.indexOf("Firefox")>0){
document.getElementById('txt1').addEventListener("input",txChange,false);
}
function txChange(){
var txt = document.getElementById('txt1');
//if(txt.value.length>1000) txt.value=txt.value.substr(0,1000);
var num = Math.floor(txt.value.length/20);
if (txt.value.length%20>0){
num = num+1;
}
alert(num);
}
</script>

<hr>

<textarea id="text" rows="5" cols="10" onkeyup="calc();"></textarea>
<input type="text" readonly="readonly" id="lines" />
<script type="text/javascript">
function calc(){
    document.getElementById('lines').value = document.getElementById('text').value.split("\n").length;
}
</script>