@charset "utf-8";
div {
  width: 800px; /* または固定幅 (例: 500px) */
  margin-left: auto;
  margin-right: auto;
  /* または短縮形 */
  /* margin: 0 auto; */
}

a:link         { color: blue;text-decoration: none;}
a:visited      { color: blue;text-decoration: none;}
a:hover        { color: blue;text-decoration: none;background-color: pink;}
body{background: url(images/bg.gif) fixed;}