Mine

		<script language="javascript">
		var text_history = [];
		var index = -1;
		
		$("#input_form").bind("submit", function(e) {
			if(e.message.value != "") {
				text_history[] = e.message.value;
				e.submit();
			}
			
			e.reset();
			e.message.focus();
			
			return (false);
		});
		
		$("#input_message").bind("keyup", function(e) {
			if(e.keyCode == 38 || e.keyCode == 40) {
				if(e.keyCode == 38) {
					index++;
				} else {
					index--;
				}
				
				ret = "";
				if(typeof text_history[index] != "undefined") {
					ret = text_history[index];
				}
				
				$(this).val(ret);
			}
		});
		
		</script>