CSS3 realizes image floating animation_html/css_WEB-ITnose

.gist {    width:220px;    height:130px;    background-image: url(2.jpg);    background-repeat:no-repeat;    border:5px solid green;    background-position:50% 50%;    transition:background-position 2s;    -moz-transition:background-position 2s; /* Firefox 4 */    -webkit-transition:background-position 2s; /* Safari and Chrome */    -o-transition:background-position 2s; /* Opera */}.gist:hover {  background-position: 50% -100px;}<div class="gist"></div>图片水平垂直居中:background-position:50% 50%;