kikan = 10;      // 日数を変更する場合はこの値を適当に

icon = "<img src='../images/new.gif' align='bottom'>";  // 適宜、サイズやalt属性を指定

today = new Date();

upday = new Date();

function koushin(y, m, d) {

   upday.setFullYear(y);

   m = m - 1;

   upday.setMonth(m);

   upday.setDate(d);

   difference = today.getTime() - upday.getTime();

   difference = Math.floor(difference / (1000 * 60 * 60 * 24));

   if (difference < kikan) {

      document.write(icon);

   }

}