Shoutbox

How would one go about doing a shoutbox/guestbook like the one at http://www.myshoutbox.com ?

It's mostly how you insert the smiley part I don't understand.

Also, how can I make it so the form doesn't redirect to the page it posts to?

guestbook.php contains the form and an iframe. the iframe contains gb.php, wich has all the entries in it. when hitting send, guestbook.php gets redirected to gb.php when it should reload only the iframe. ideas?