function randomImg(){
	
	n_img_folder = 8;
	n_img_to_rotate = 4;
	n_img = 0;
	str_img = "|";
	
	while (n_img<n_img_to_rotate){
		i = Math.round((n_img_folder-1)*Math.random());
		
		if (str_img.indexOf("|"+i+"|") == -1){
			str_img = str_img + i +"|";
			++n_img;
		}
	}
	
	str_img = str_img.substr(1);
	str_img = str_img.substr(0,str_img.length-1);
	arr = str_img.split("|")
	str = ""
	for (var i=0; i < arr.length; i++) {
		n = '0'+(i+1);
		id_name='immagine' + n.substr(-2,2);
		n = '0'+(parseInt(arr[i])+1);
		img_name = 'immagine' + n.substr(-2,2);
		img_name = '/imgrotate/'+img_name+'.jpg'
		str = str + id_name+ " ->" + img_name + "\n";
		//alert(id_name+ " ->" + img_name);
		document.getElementById(id_name).src = img_name;
 	}
	
}