var stylemac    = 'mac.css';  //for mac
var styleWinIE  = 'win_ie.css';  //for win_ie
var styleWinNN  = 'win_nn.css';  //for win_nn
var styleWinNN6 = 'win_nn6.css'; //for win_nn6
if (!navigator.platform.match(/win/i)){
 var style = stylemac;
}else{
 if (navigator.appName.match(/microsoft/i)){
  var style = styleWinIE;
 }else{
  if( document.getElementById ){
   var style = styleWinNN6;
  }else{
   var style = styleWinNN;
  }
 }
}
document.write('<link rel="stylesheet" href="css/'+style+'" type="text/css">');