function findimg() {
	var imgs,i,src,ftype,preloadsrc;
	imgs=document.getElementsByTagName('img');
	for (i=0;i<imgs.length;i++) {
		if (/roll/.test(imgs[i].className)) {
			//preload
			src = imgs[i].src;
			ftype = src.substring(src.lastIndexOf('.'), src.length);
			preloadsrc = src.replace(ftype, '_on'+ftype);
			imgs[i].preloadpic = new Image();
			imgs[i].preloadpic.src = preloadsrc;
			//alert(imgs[i].preloadpic + " has the src: " + preloadsrc);
			//mouse behaviour
			imgs[i].onmouseover=function(){roll(this);};
			imgs[i].onmouseout=function(){roll(this);};
		}
	}
}

function roll(o) {
	var src,ftype,newsrc;
	src = o.src;
	ftype = src.substring(src.lastIndexOf('.'), src.length);
	if (/_on/.test(src)) { //off
		newsrc = src.replace('_on','');
	} else { //over
		newsrc = src.replace(ftype, '_on'+ftype);
	}
	o.src=newsrc;
}

window.onload=function(){
	findimg();
}