function getOSType()
{
    var uAgent  = navigator.userAgent.toUpperCase();
    if (uAgent.indexOf("MAC") >= 0) return "Mac";
    if (uAgent.indexOf("WIN") >= 0) return "Windows";
    return "";
}


function getBrowserName()
{
    var uaName  = navigator.userAgent.toUpperCase();
	if (uaName.indexOf("FIREFOX",0) > -1) return "firefox";
	if (uaName.indexOf("SAFARI",0) > -1) return "safari";
	if (uaName.indexOf("OPERA",0) > -1) return "opera";
	if (uaName.indexOf("MSIE",0) > -1) return "ie";
	if (uaName.indexOf("NETSCAPE",0) > -1) return "nn";
    return "";
}

var cssDir = 'http://blog.shizuokaonline.com/shiozawa/css/os/';
var cssTags = '<link rel="stylesheet" type="text/css" href="';
os = getOSType();
browser = getBrowserName();
if (os == "Mac")   fileName = "mac";
if (os == "Windows") fileName = "win";
if (browser == "firefox") fileName += "firefox";
if (browser == "safari") fileName += "safari";
if (browser == "opera") fileName += "opera";
if (browser == "nn") fileName += "nn";
if (browser == "ie") fileName += "ie";
document.write(cssTags+cssDir+fileName+'.css">');