Edit in JSFiddle

<a href="#" class="btn">First Button</a>
<hr>
<a href="#" class="btn btn-small">Second Button</a>
<hr>
<a href="#" class="btn btn-large">Third Button</a>

html{
    font: 1em/1.5 "Helvetica Neue", Arial, sans-serif;
}

.btn{
    display: inline-block;
    padding: .5em 1em;
    text-decoration: none;
    color: #06c;
    background-color: #ededed;
    border-radius: .2em;
}

.btn-small{
    font-size: .8rem;
}

.btn-large{
    font-size: 2rem;
}

hr{
    height: 0;
    border: 0;
    border-bottom: 1px solid #ededed;
}