<div class="wrap">
<input type="text" id="name-user">
<label for="name-uzer">ФИО</label>
<span>С больших букв</span>
</div>
input {
display: block;
width: 200px;
border: none;
font-size: 15px;
border-bottom: 2px solid black;
}
.wrap {
padding: 30px;
position: relative;
margin: 50px;
}
label {
position: absolute;
top: 30px;
left: 30px;
font-size: 20px;
}
input:focus ~ label {
font-size: 10px;
top: 10px;
}