$usr=$_SERVER['HTTP_USER_AGENT'];
$firefoxam = 'firefox.png';
$ie = 'ie.png';
$cits = 'cits.png';
if(eregi("Firefox", $usr)){ echo '<img src="'.$firefoxam.'" alt="firefox"/>' }
else if(eregi("IE", $usr)){ echo '<img src="'.$ie.'" alt="ie"/>' }
else { echo '<img src="'.$cits.'" alt="cits"/>'; }