function logo_change (){

var length = 21;
var ran_num = Math.round((length-1)*Math.random());

ran_num=ran_num+1;

var source1 = "rotaz/"+ran_num+".jpg";


if(document.images['logo1']) {
  document.images['logo1'].src = source1;
}
var length = 494;

for (var i=1; i <= 4; i ++) {
	var ran_num = Math.round((length-1)*Math.random());
	ran_num=ran_num+1;
	var href = "big/"+ran_num +"_b.jpg";
	source1 = "photo/"+ran_num+".jpg";
if(document.images['pic'+i]) {
  document.images['pic'+i].src = source1;
  document.links['link'+i].href = href;
}


}

}