var stylemac    = '/file.jsp?id=5272';  //for mac
var styleWinIE  = '/file.jsp?id=5273';  //for win_ie
var styleWinNN  = '/file.jsp?id=5274';  //for win_nn
var styleWinNN6 = '/file.jsp?id=5275'; //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="'+style+'" type="text/css">');