if (document.images)   {
   m1_off = new Image(); m1_on = new Image();
   m2_off = new Image(); m2_on = new Image();
   m3_off = new Image(); m3_on = new Image();
   m4_off = new Image(); m4_on = new Image();
   m5_off = new Image(); m5_on = new Image();
   m6_off = new Image(); m6_on = new Image();
   m7_off = new Image(); m7_on = new Image();

   m1_off.src = "img/m1_off.gif";
   m1_on.src = "img/m1_on.gif";
   m2_off.src = "img/m2_off.gif";
   m2_on.src = "img/m2_on.gif";
   m3_off.src = "img/m3_off.gif";
   m3_on.src = "img/m3_on.gif";
   m4_off.src = "img/m4_off.gif";
   m4_on.src = "img/m4_on.gif";
   m5_off.src = "img/m5_off.gif";
   m5_on.src = "img/m5_on.gif";
   m6_off.src = "img/m6_off.gif";
   m6_on.src = "img/m6_on.gif";
   m7_off.src = "img/m7_off.gif";
   m7_on.src = "img/m7_on.gif";

}

// Function to 'OnOff' images.
function OnOff(imgName) {
var n=7;
   if (document.images) {
            for (var i=1;i<=n;i++){
                                var nm = "m"+i;
                                if (imgName == nm){
                                document[nm].src = eval(imgName + "_on.src");
                                }
                                else {
                                document[nm].src = eval(imgName + "_off.src");
                                }
                          }
   }
}

// Function to 'activate' images.
function imgOn(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "_on.src");
        }
}

// Function to 'deactivate' images.
function imgOff(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "_off.src");
        }
}