browser_name = navigator.appName;
browser_version = parseFloat(navigator.appVersion);

if (browser_name == "Netscape" && browser_version >= 3.0) { browser_ok = 'true'; }
else if (browser_name == "Microsoft Internet Explorer" && browser_version >= 3.0) { browser_ok = 'true'; }
else { browser_ok = 'false'; }

function change(img, ref) {
   if (browser_ok == 'true') {
       document.images[img].src = ref;
   }
}

if (browser_ok == 'true'){
	a1=new Image; a1.src="images/m_1a.gif";
	a2=new Image; a2.src="images/m_2a.gif";
	a3=new Image; a3.src="images/m_3a.gif";
	a4=new Image; a4.src="images/m_4a.gif";
	a5=new Image; a5.src="images/m_5a.gif";
	a6=new Image; a6.src="images/dott_m_a.gif";
}