if(document.images) {
pics = new Array(); 
pics[1] = new Image();
pics[1].src = "/images/bt_home1.gif"; 
pics[2] = new Image();
pics[2].src = "/images/bt_home2.gif";
pics[3] = new Image();
pics[3].src = "/images/bt_prd1.gif";
pics[4] = new Image();
pics[4].src = "/images/bt_prd2.gif";
pics[5] = new Image();
pics[5].src = "/images/bt_whatplus1.gif";
pics[6] = new Image();
pics[6].src = "/images/bt_whatplus2.gif";
pics[7] = new Image();
pics[7].src = "/images/bt_contact1.gif";
pics[8] = new Image();
pics[8].src = "/images/bt_contact2.gif";
pics[9] = new Image();
pics[9].src = "/images/bt_classes1.gif";
pics[10] = new Image();
pics[10].src = "/images/bt_classes2.gif";
}

function changer(from,to) {
if(document.images) {
document.images[from].src = pics[to].src;
}
}