var smf_images_url = "http://www.usanie-uangu.com/smf/Themes/usanie/images";

function invert() {
         document.getElementById("formbox").className = document.getElementById("formbox").className == 'show'?'hide':'show' ;
         document.getElementById("img_01").src = document.getElementById("img_01").src == smf_images_url + "/expand.gif" ? smf_images_url + "/collapse.gif" : smf_images_url + "/expand.gif";
}