if(navigator.appVersion.charAt(0) >= 3){
var img = new Array();
img[0]=new Image();img[0].src = "images/bt.gif";
img[1]=new Image();img[1].src = "images/bt_ro.gif";
}
function change_image(nam,num){
if(navigator.appVersion.charAt(0) >= 3){
document.images[nam].src = img[num].src;
}
}