if (navigator.userAgent.indexOf("Win") >= 0) {
		if (vercheck(1,0)) {
				document.write('<LINK REL="stylesheet" TYPE="text/css" HREF="css/win_ie.css">')
		} else {
				document.write('<LINK REL="stylesheet" TYPE="text/css" HREF="css/win_nn.css">')
		}
} else {
		document.write('<LINK REL="stylesheet" TYPE="text/css" HREF="css/mac.css">')
}

function vercheck(IEversion,NNversion) {
	if ((navigator.appName.indexOf("Microsoft") >= 0)
		&&(IEversion != 0)
		&&(IEversion <= parseFloat(navigator.appVersion))) {
		return true
	} else {
		if ((navigator.appName.indexOf("Netscape") >= 0)
			&&(NNversion != 0)
			&&(NNversion <= parseFloat(navigator.appVersion))) {
			return true
		} else {
			return false
		}
	}
}
<!--

function newImage(arg) {
	if (document.images) {
		rslt = new Image();
		rslt.src = arg;
		return rslt;
	}
}

function changeImages() {
	if (document.images && (preloadFlag == true)) {
		for (var i=0; i<changeImages.arguments.length; i+=2) {
			document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
		}
	}
}

var preloadFlag = false;
function preloadImages() {
	if (document.images) {
		home_over = newImage("images/home-over.gif");
		preloadFlag = true;
	}
}


function OpenMenu(id){ 
   document.getElementById( id ).style.visibility = 'visible';
}
function CloseMenu(id){
   document.getElementById( id ).style.visibility = 'hidden';
}