This is the code I use. It's simple and it works in ePub2 and ePub3.
HTML
Code:
<div class="cover">
<img alt="" class="cover" src="../images/MSRCover.jpg"/>
</div>
CSS
Code:
body {
widows: 1;
orphans: 1;
margin-top: 0;
margin-right: 0;
margin-bottom: 0;
margin-left: 0;
text-align: justify;
}
img {
max-height: 100%;
max-width: 100%;
}
.cover {
text-align: center;
text-indent: 0;
height: 100%;
}