body {
  margin: 0;
  padding: 0;
}

#main {
  margin: 8px;
}

h1, h2, h3, p {
  margin: 12px 16px; /* 上下、左右 */
}

ul {
  padding-left: 2em;
  line-height: 150%;
}

table {
  margin: 12px 2em;
  padding: 4px;
  border-collapse: collapse;
  line-height: 150%;
  white-space: nowrap;
}

th {
  background: #f0f0f0;
  border: 1px solid gray;
  padding: 4px 8px;
  text-align: left;
}

td {
  background: #ffffff;
  border: 1px solid gray;
  padding: 2px 8px;
}