#login_box {
  float: right;
  background: red;
}

#register_box {
  padding: 16px;
}

#register_box input[type="text"] {
  width: 100%;
}
#register_box input[type="password"] {
  width: 100%;
}

table, th, td {
  border: 1px solid black;
  border-collapse: collapse;
}
th, td {
  padding: 5px;
}