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 >= 3.0) { roll = 'true'; }
else { roll = 'false'; }
function over(img,ref) { if (roll == 'true') { document.images[img].src = ref; } }
function out(img,ref)  { if (roll == 'true') { document.images[img].src = ref; } }