//declare and load images.
if (document.images) {
	img1on = new Image(100,51) ;
	img1on.src="../nav/btna_on.gif" ;
	img2on = new Image(100,51) ;
	img2on.src="../nav/btnb_on.gif" ;
	img3on = new Image(100,51) ;
	img3on.src = "../nav/btnc_on.gif" ;
	img4on = new Image(100,51) ;
	img4on.src = "../nav/btnh_on.gif" ;
	img5on = new Image(60,50) ;
	img5on.src = "../nav/btnnext_on.gif" ;
	img6on = new Image(100,51) ;
	img6on.src = "../nav/btnret_on.gif" ;

	img1off = new Image(100,51) ;
	img1off.src="../nav/btna_off.gif" ;
	img2off = new Image(100,51) ;
	img2off.src="../nav/btnb_off.gif" ;
	img3off = new Image(100, 51) ;
	img3off.src = "../nav/btnc_off.gif" ;
	img4off = new Image(100, 51) ;
	img4off.src = "../nav/btnh_off.gif" ;
	img5off = new Image(60, 50) ;
	img5off.src = "../nav/btnnext_off.gif" ;
	img6off = new Image(100, 51) ;
	img6off.src = "../nav/btnret_off.gif" ;

	img1ad = new Image(100,100) ;
	img1ad.src="../nav/btna_desc.gif" ;
	img2ad = new Image(100,100) ;
	img2ad.src="../nav/btnb_desc.gif" ;
	img3ad = new Image(100,100) ;
	img3ad.src = "../nav/btnc_desc.gif" ;
	img4ad = new Image(100,100) ;
	img4ad.src = "../nav/btnnul_desc.gif" ;
	img5ad = new Image(100,100) ;
	img5ad.src = "../nav/btnnul_desc.gif" ;
	img6ad = new Image(100,100) ;
	img6ad.src = "../nav/btnret_desc.gif" ;
}

//function to activate images.
function imgOn(imgName) {
	if (document.images) {
		document[imgName].src = eval (imgName + "on.src") ;
		document["desc"].src = eval (imgName + "ad.src") ;
	}
}

//function to deactivate images.
function imgOff(imgName) {
	if (document.images) {
		document[imgName].src = eval (imgName + "off.src") ;
		document["desc"].src = "../nav/btnnul_desc.gif" ;
	}
}