kikan = 3;      // 日数を変更する場合はこの値を適当に
icon = "<img src=http://creativefreaks.net/images/new/new022_11.gif" width="32" height="16" alt="CreativeFreaks.NET" />";  // 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);
   }
}