var loaded = 0;
var ope = navigator.userAgent.toLowerCase()

if (navigator.appVersion.indexOf('Win') != -1)
{
if (loaded != 1 && parent.document.layers)
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/netscape4.css'>";
document.write(cssaufruf.toString());
loaded =1;
}

if (loaded != 1 && navigator.appName == "Microsoft Internet Explorer")
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/explorer.css'>";
document.write(cssaufruf.toString());
loaded =1;
}

if (loaded != 1 && document.getElementById)
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/netscape6.css'>";
document.write(cssaufruf.toString());
loaded =1;
}

if (ope.indexOf('opera') > -1)
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/explorer.css'>";
document.write(cssaufruf.toString());
loaded =1;
}

if (loaded != 1)
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/explorer.css'>";
document.write(cssaufruf.toString());
alert('win');
}
}

if (navigator.appVersion.indexOf('Macintosh') != -1)
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/mac.css'>";
document.write(cssaufruf.toString());
}

if (navigator.appVersion.indexOf('Linux') != -1)
{
var cssaufruf = "<LINK REL=STYLESHEET TYPE='text/css' HREF='styles/explorer.css'>";
document.write(cssaufruf.toString());
}