body {
    color: #333333;
    background-color: #34495e;
    font: 100%/1.4em "Helvetica Neue", "Helvetica", "Arial", sans-serif;
    text-align: center;
    -webkit-text-size-adjust: none;
}

h1 {
    color: #FFF;
    font-size: 4em;
    font-weight: normal;
    line-height: 1.2em;
    margin: 0 auto;
    padding: 10px 20px;
    position: relative;
    text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.5);
    width: 60%;
}

.heart {
    color: #c0392b;
    display: inline-block;
    font-style: normal;
    font-weight: 500;
    font-size: 476px;
    margin-top: .3em;
}

body {
    color: #333333;
    background-color: #34495e;
    font: 100%/1.4em "Helvetica Neue", "Helvetica", "Arial", sans-serif;
    text-align: center;
    -webkit-text-size-adjust: none;
}

h1 {
    color: #FFF;
    font-size: 4em;
    font-weight: normal;
    line-height: 1.2em;
    margin: 50px auto 20px;
    padding: 10px 20px;
    position: relative;
    text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.5);
    width: 60%;
}

.heart {
    color: #c0392b;
    display: inline-block;
    font-style: normal;
    font-weight: 500;
    font-size: 476px;
    margin-top: .3em;
}

Update margin property on h1 tag.
Update margin property on h1 tag.