//ブラウザチェック
if(navigator.userAgent.indexOf("Win")!=-1)
{
//Win用の命令をここに書く
platform = 'Win';
document.write("<link rel='stylesheet' href='win.css' type='text/css'>");
}
else if(navigator.userAgent.indexOf("Mac")!=-1)
{
//Mac用の命令をここに書く
platform = 'Mac';
document.write("<link rel='stylesheet' href='mac.css' type='text/css'>");
}