// 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('>')