function select_image(n, t, url) {
	var a;

	// switch the large image	
	document.images['big'].src = url;

	for(i=1; i<=t; i++) {
		a = 'a' + i;
		
		document.getElementById(a).style.backgroundPosition= "0px 0px";
	}
	
	a = 'a' + n;
	document.getElementById(a).style.backgroundPosition= "64px 0px";
	
	//alert(n);
	//document.images[s].src = '/images/portfolio1/thumbs/p1_t1b.jpg';
}