keyDown :
<html>
<body>
<script type="text/javascript">
function keyFilter(e, field) {
var key = window.event ? e.keyCode : e.which;
if (key == 9) {
field.value += "\t";
return false;
}
return true;
}
</script>
<form>
<textarea onkeydown="return keyFilter(event, this);"></textarea>
</form>
</html>
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