if (parseInt(navigator.appVersion) >= 3) {

 button1_off = new Image;
 button1_off.src = "images/button_off.gif";
 button1_on = new Image;
 button1_on.src = "images/button_on.gif";

 button2_off = new Image;
 button2_off.src = "images/button_off.gif";
 button2_on = new Image;
 button2_on.src = "images/button_on.gif";

 button3_off = new Image;
 button3_off.src = "images/button_off.gif";
 button3_on = new Image;
 button3_on.src = "images/button_on.gif";

 button4_off = new Image;
 button4_off.src = "images/button_off.gif";
 button4_on = new Image;
 button4_on.src = "images/button_on.gif";

}

 function img_act(img_name) {
      if (parseInt(navigator.appVersion) >= 3) {
           img_on = eval(img_name + "_on.src");
           document [img_name].src = img_on;
      }
 }


 function img_inact(img_name) {
      if (parseInt(navigator.appVersion) >= 3) {
           img_off = eval(img_name + "_off.src");
           document [img_name].src = img_off;
      }
 }