l'invio del form puoi risolverlo così:

<script language="JavaScript">
function updateTextArea(){
txt = document.form.txtarea.value;
arr = txt.split("\r");
if(arr.length>2)
alert("TROPPE RIGHEEEEEEEEEEEE");
else
document.form.submit()
}
</script>
<html>
<form name="form">
<textarea name="txtarea"></textarea>
<input type="button" value="click" onclick="updateTextArea()">
</form>
</html>