intl-tel-input/build/css/demo.css

A JavaScript plugin for entering and validating international telephone numbers

* {
  box-sizing: border-box;
}

body {
  margin: 20px;
  font-size: 14px;
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  color: #555;
}

input,
.button {
  height: 35px;
  margin: 0;
  padding: 6px 12px;
  border-radius: 2px;
  font-family: inherit;
  font-size: 100%;
  color: inherit;
}
input[disabled],
.button[disabled] {
  background-color: #eee;
}

input,
select {
  border: 1px solid #ccc;
  width: 220px;
}

input::placeholder {
  color: #bbb;
}

.button {
  color: #fff;
  background-color: #428bca;
  border: 1px solid #357ebd;
  margin-left: 5px;
}
.button:hover {
  background-color: #3276b1;
  border-color: #285e8e;
  cursor: pointer;
}

.notice {
  margin-top: 15px;
}