function isNetscape() {
	return (navigator.appName == "Netscape");
}
function isOpera() {
	return (navigator.userAgent.indexOf("Opera")!=-1);
}
function isNetscape4() {
	return (isNetscape() && navigator.appVersion.charAt(0) == "4");
}
function isNetscape6() {
 	return (isNetscape() && navigator.appVersion.charAt(0) != "4");
}
function isExplorer() {
	return (!isNetscape() && !isOpera());
}
function isExplorer4() {
	return isExplorer();
}
function isMac() {
	return (navigator.appVersion.lastIndexOf('Mac')!=-1)
}