html,
body {
  background-color: #fff;
  width: 728px;
  height: 90px;
  margin: 0;
  overflow: hidden;
  box-sizing: border-box;
}

body {
  border: 1px solid grey;
}

a {
  width: 728px;
  height: 90px;
}

#bm {
  width: 728px;
  height: 90px;
  cursor: pointer;
  background: #fff;
}