body {
    font-family: sans-serif;
}

iframe {
    width:100%;
    float: left;
}
.form-group {
    height: 40px;
}
h2 {
    margin: 7px 0;
}
#ss-card,
#ss-date,
#ss-cvv {
    height: 85px;
}
#ss-card {
    margin-bottom: 55px;
    display: block;
}
#ss-date {
    float: left;
    display: block;
}
#ss-cvv.form-group {
    float: right;
}
.iframeholder {
    width:100%;
}
.ie8 form .iframeholder {
    padding: 10px;
}
.iframeholder::after {
    content: '';
    display: block;
    width: 100%;
    height: 0px;
    clear: both;
    position: relative;
}
.ie8 form .form-group {
    margin-bottom: 5px;
}
textarea {
    padding: 10px;
    font-family: sans-serif;
}
label[for=iframesCardNumber],
label[for=iframesCardExpiration],
label[for=iframesCardCvv] {
    text-transform: uppercase;
    font-weight: 500;
    font-size: 13px;
    color: #555;
    line-height: 1.5;
}
.ie8 form label {
    padding-left: 10px;
    margin: 0px;
}
#heartland-frame-cardExpiration,
#heartland-frame-cardCvv,
#heartland-frame-cardNumber,
.ie8 #heartland-frame-cardExpiration,
.ie8 #heartland-frame-cardCvv,
.ie8 #heartland-frame-cardNumber {
    width: 100%;
}
iframe {
    margin: 0;
    padding: 0;
    border: none;
    width: value;
    height: value;
}
#ss-banner {
    background: transparent url(images/ss-shield@2x.png) no-repeat left center;
    height: 40px;
    background-size: 280px 34px;
    margin-bottom: 7px;
}
.ie8 #ss-banner {
    background: transparent url(images/ss-shield-ie.png) no-repeat left center;
}
.btn-primary {
    display: block;
    border-radius: 0px;
    font-size: 18px;
    float: right;
    background-color: #36b46e;
    border: 1px solid #2a8d56;
    margin-bottom: 10px;
    height: 50px;
    color: #ffffff;
    width: 100%;
}
.btn-primary:hover,
.btn-primary:focus {
    color: #fff;
    background-color: #2a8d56;
}
.ie8 .btn-primary {
    width: 15%;
}
.red {
    color: #ce2027;
    margin-left: 2px;
    font-size: 17px;
}
.container {
    margin: 5px;
}
#ss-date.form-group,
#ss-cvv.form-group {
    width: 100%;
}
@media screen and (min-width: 767px) {
    #heartland-frame-cardNumber {
        width: 100%;
    }
}
@media screen and (min-width: 696px) {
    #ss-date.form-group,
    #ss-cvv.form-group {
        width: 48%;
    }
}
@media screen and (min-width: 636px) {
    #ss-card {
        margin-bottom: 40px;
    }
}
@media screen and (min-width: 450px) {
    .btn-primary,
    .ie8 .btn-primary {
        width: 10em;
    }
    .container {
        margin: 20px;
    }
}

#ss-banner {
    background: transparent url(https://github.com/hps/heartland-php/blob/master/examples/end-to-end/assets/images/ss-shield@2x.png?raw=true) no-repeat left center;
    height: 40px;
    background-size: 280px 34px;
    margin-bottom: 7px;
}

user agent stylesheet
div {
    display: block;
}

.form-row {
    margin-top: 10px;
}

.form-wrapper {
    display: block;
    width: 300px;
    margin: 10px auto;
}