if (document.images)
        {
                btn1a=new Image()
                btn1a.src="m_btn1.gif"
                btn1b=new Image()
                btn1b.src="m_btn1a.gif"
                
                btn2a=new Image()
                btn2a.src="m_btn2.gif"
                btn2b=new Image()
                btn2b.src="m_btn2a.gif"

                btn3a=new Image()
                btn3a.src="m_btn3.gif"
                btn3b=new Image()
                btn3b.src="m_btn3a.gif"

                btn4a=new Image()
                btn4a.src="m_btn4.gif"
                btn4b=new Image()
                btn4b.src="m_btn4a.gif"
 
                btn5a=new Image()
                btn5a.src="m_btn5.gif"
                btn5b=new Image()
                btn5b.src="m_btn5a.gif"
                
                btn6a=new Image()
                btn6a.src="bnt1a.gif"
                btn6b=new Image()
                btn6b.src="bnt1.gif"    
                }
function imgOff(imgName)
        {
                if  (document.images);
        {
                document[imgName].src = eval (imgName + "a.src");
        }
}

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


<!--

imgprodon=new Image();
imgprodon.src="m_btn1a.gif";
imgprodoff=new Image();
imgprodoff.src="m_btn1.gif";

imgfacilityon=new Image();
imgfacilityon.src="m_btn2a.gif";
imgfacilityoff=new Image();
imgfacilityoff.src="m_btn2.gif";

imgconon=new Image();
imgconon.src="m_btn3a.gif";
imgconoff=new Image();
imgconoff.src="m_btn3.gif";

//-->