.heading{
    margin-left:auto;
    margin-right:auto;
    text-align: center;
    margin-top:24px;
    width:500px;
    margin-bottom:6px;
}

.left_button img{
    float:right;
    margin-top:15px;
    margin-bottom:15px;
}
.left_button a:hover img {
    -moz-opacity:0.7;
    opacity:0.7;
    filter: alpha(opacity=70);
}