// OS

  var Win = navigator.userAgent.indexOf("Win") != -1 ? true : false 

  var Mac = navigator.userAgent.indexOf("Mac") != -1 ? true : false 

  var X11 = navigator.userAgent.indexOf("X11") != -1 ? true : false 

  

  if (document.getElementById) {

  

    if (Win) cssurl = "/css/win.css"  // Win W3C

    else if(Mac) cssurl = "/css/mac.css"  // Mac W3C

    else if(X11) cssurl = "/css/win.css"  // X11 W3C

  

  } else if (document.all) {

  

    if (Win) cssurl = "/css/win.css"  // Win IE

    else if(Mac) cssurl = "/css/mac.css"  // Mac IE

  

  } else if (document.layers) {

  

    if (Win) cssurl = "/css/win.css"  // Win N4

    else if(Mac) cssurl = "/css/mac.css"  // Mac N4

    else if(X11) cssurl = "/css/win.css"  // X11 N4

  

  } else {

    cssurl ="/css/win.css"  // other

  }

  

  //output

  document.write('<link rel="stylesheet" ')

  document.write('      type="text/css"  ')

  document.write('      href="'+cssurl+'"')

  document.write('>')