browser_name = navigator.appName;
browser_version = parseFloat(navigator.appVersion); 
if (browser_name == "Netscape" && browser_version >= 3.0) { roll = 'true'; }
else
if (browser_name == "Microsoft Internet Explorer" && browser_version >= 4.0) { roll = 'true'; }
else { roll = 'false';}

function najed(img1,ref1) { if (roll == 'true') 
        { 	document.images[img1].src = ref1;}    
        }
function vodjed(img1,ref1) { if (roll == 'true')  
        { 	document.images[img1].src = ref1;  	 }}