if (document.images)
   {
     pic1on= new Image;
     pic1on.src="images/homeon.gif"; 
	 pic2on= new Image;
     pic2on.src="images/galleryon.gif";
	 pic3on= new Image;
     pic3on.src="images/profileon.gif";
	 pic4on= new Image;
     pic4on.src="images/contacton.gif";
	 
     pic1off= new Image;
     pic1off.src="images/homeoff.gif";
	 pic2off= new Image;
     pic2off.src="images/galleryoff.gif";
	 pic3off= new Image;
     pic3off.src="images/profileoff.gif";
	 pic4off= new Image;
     pic4off.src="images/contactoff.gif";
   }

function lightup(imgName)
 {
   if (document.images)
    {
      imgOn=eval(imgName + "on.src");
      document[imgName].src= imgOn;
    }
 }

function turnoff(imgName)
 {
   if (document.images)
    {
      imgOff=eval(imgName + "off.src");
      document[imgName].src= imgOff;
    }
 }