Div behind the input

.holder {
    position: relative;
}
.dropdown {
    position: absolute;
    border: 1px solid red;
    display: none;
}

input:focus + .dropdown {
    display: block;
}



<div class="holder">
    <input type="text" />
    <div class="dropdown">
        <p>Testing</p>
        <p>Css ONLY</p>
        <p>Dropdown</p>
    </div>
</div>

//source http://jsfiddle.net/gx8f2zeu/

just like facebox