<form class="form">
<input placeholder="Текст">
</form>
CSS
.form {
text-align: center;
}
input {
border-left: 0;
border-right: 0;
border-top: 0;
border-bottom-width: 2px;
border-bottom-color: #000;
outline: none;
padding: 10px 0;
}
input::placeholder {
text-align: center;
color: #82868E;
font-size: 15px;
}