var randObjects=[
'<img src="http://grid-od.com/blog/css/form_img/001.jpg" width="381">',
'<img src="http://grid-od.com/blog/css/form_img/002.jpg" width="381">'
];
function randFormimg() {
var rr = parseInt(Math.random() * randObjects.length);
document.write(randObjects.slice(rr,rr+1)[0]);
}