<form method="get" action="<? echo $site_url?>/index.php" onsubmit="location.href='<? echo $site_url?>/'+encodeURIComponent(this.q.value).replace(/%20/g, '+')+'.html'; return false;">

	    <input name="q" type="text" value="<?=$q?>"/>
		<input type="submit" value="Go" />
</form>