body {
    margin: 0px;
}

.btn {
    font-size: 14px;
    font-weight: 400;
    color: #fff;
    background: rgb(0, 153, 0);
    border: 2px solid rgb(0, 153, 0);
    -webkit-transition: all 0.2s ease-in-out; /* Chrome 1-25, Safari 3.2+ */
    -moz-transition: all 0.2s ease-in-out; /* Firefox 4-15 */
    -o-transition: all 0.2s ease-in-out; /* Opera 10.50?12.00 */
    transition: all 0.2s ease-in-out; /* Chrome 26, Firefox 16+, IE 10+, Opera 12.10+ */
    width: 190px;
    height: 48px;
    cursor: pointer;
}

.btn:hover {
    color: rgb(0, 153, 0);
    background: #fff;
    border: 2px solid rgb(0, 153, 0);
}

.btn:before {
    display: inline-block;
    width: 32px;
    height: 32px;
    margin-right: 5px;
    content: "";
    background: url('../img/icon_unID_4.png') no-repeat 0 0;
    background-size: 100%;
    vertical-align: middle;
    -webkit-transition: all 0.2s ease-in-out; /* Chrome 1-25, Safari 3.2+ */
    -moz-transition: all 0.2s ease-in-out; /* Firefox 4-15 */
    -o-transition: all 0.2s ease-in-out; /* Opera 10.50?12.00 */
    transition: all 0.2s ease-in-out; /* Chrome 26, Firefox 16+, IE 10+, Opera 12.10+ */
}

.btn:hover:before {
    display: inline-block;
    width: 32px;
    height: 32px;
    margin-right: 5px;
    content: "";
    background: url('../img/icon_unID_3.png') no-repeat 0 0;
    background-size: 100%;
    vertical-align: middle;
    -webkit-transition: all 0.2s ease-in-out; /* Chrome 1-25, Safari 3.2+ */
    -moz-transition: all 0.2s ease-in-out; /* Firefox 4-15 */
    -o-transition: all 0.2s ease-in-out; /* Opera 10.50?12.00 */
    transition: all 0.2s ease-in-out; /* Chrome 26, Firefox 16+, IE 10+, Opera 12.10+ */
}