if(-1 != navigator.userAgent.indexOf("MSIE"))
    { 
    document.write('<link rel="stylesheet" type="text/css" href="ie.css">');
    }
    else if (-1 != navigator.userAgent.indexOf("Mozilla"))
    {
    // Netscape
    document.write('<link rel="stylesheet" type="text/css" href="nc.css">');
    }
    else
    {
    // other
    document.write('<link rel="stylesheet" type="text/css" href="inny.css">');
    }