Something

<?php
$nick = trim($_POST["nick"]);
if ( isset($_POST["nick"]) ) {
	if (strlen($nick) <= 3) { ?>
		<div id="notice" style="font-weight:bold;">Nickname must be atleast 4 characters in length.</div>
		<hr />
		<div id="note">Enter a nickname:</div>
		<form method="post" action="chat.php" onsubmit="send_nick(this); return false;">
			<input type="text" name="n" size="30" />
			<input type="submit" value="Continue ->" name="btnSubmit" />
		</form>
	<? } else { ?>
		<div id="notice" style="font-weight:bold;">Hello <? echo strtolower($nick) ?>, Welcome to the chat.</div>
		<hr />
		<div id="container">
			<div id="chat"></div>
		</div>
		<div id="sndText">
			<form id="sndText" method="post" action="chat.php" onsubmit="change('chat',this); return false;">
				<input type="text" name="ctext" size="30" />
				<input type="submit" value="Send" name="btnSend" />
			</form>
		</div>
		<br />
	<? } ?>
<? } ?>