if (/Firefox\/(\d+\.\d+)/.test(navigator.userAgent)){ 
var browser_version=new Number(RegExp.$1);
if (browser_version<=4) {
	location.replace('http://www.mozilla.org/en-US/firefox/new/');
	window.alert("You are using an older version Firefox which is no longer supported by this website. Please update to view this site.");
	}
}

if (/MSIE (\d+\.\d+)/.test(navigator.userAgent)){ 
var browser_version=new Number(RegExp.$1);
if (browser_version<=6) {
	location.replace('http://windows.microsoft.com/en-GB/internet-explorer/downloads/ie');
	window.alert("You are using an older version of Internet Explorer which is no longer supported by this website. Please update to view this site.");
	}
}