Vertical CSS3 carousel

Vertical images carousel with pure CSS3.

HTML

<div class="scrollable" style="float:left;">
    <div class="itemsup">
        <img src="http://farm8.staticflickr.com/7020/6767599565_e0ffee2813_d.jpg" alt="" />
        <img src="http://farm8.staticflickr.com/7016/6767598507_21720ed21f_d.jpg" alt="Seven to ten at Leeds & Holbeck" />
        <img src="http://farm8.staticflickr.com/7163/6767596393_8f8b9609ec_d.jpg" alt="Seven to ten at Leeds & Holbeck" />
    </div>
</div>

<div class="scrollable" style="float:left;">
    <div class="itemsdown">
        <img src="http://farm8.staticflickr.com/7020/6767599565_e0ffee2813_d.jpg" alt="" />
        <img src="http://farm8.staticflickr.com/7016/6767598507_21720ed21f_d.jpg" alt="Seven to ten at Leeds & Holbeck" />
        <img src="http://farm8.staticflickr.com/7163/6767596393_8f8b9609ec_d.jpg" alt="Seven to ten at Leeds & Holbeck" />
    </div>
</div>

CSS

body {
    padding: 1em;
    background: #999
}
.scrollable {
    height: 500px;
    width: 333px;
    margin: 0 auto;
    padding: 0;
    border:10px solid #fff;
    background: #000;
    position: relative;
    overflow: hidden;
    text-align: center;
}
img {
    max-height: 500px;
    margin: 0 auto;
    display: block;
}
.itemsup {
    -webkit-animation: scrollup 12s infinite;
    -moz-animation: scrollup 12s infinite;
    -ms-animation: scrollup 12s infinite;
}
.itemsdown {
    -webkit-animation: scrolldown 12s infinite;
    -moz-animation: scrolldown 12s infinite;
    -ms-animation: scrolldown 12s infinite;
}

@-webkit-keyframes scrolldown {
  0%   { margin-top: -1000px; }
27.33%  { margin-top: -1000px; }
  33.33%  { margin-top: -500px; }
60.66% { margin-top: -500px; }
66.66% { margin-top: 0px; }
94.99% { margin-top: 0px; }
  100%  { margin-top: -1000px; }
}
@-moz-keyframes scrolldown {
  0%   { margin-top: -1000px; }
27.33%  { margin-top: -1000px; }
  33.33%  { margin-top: -500px; }
60.66% { margin-top: -500px; }
66.66% { margin-top: 0px; }
94.99% { margin-top: 0px; }
  100%  { margin-top: -1000px; }
}
@-ms-keyframes scrolldown {
  0%   { margin-top: -1000px; }
27.33%  { margin-top: -1000px; }
  33.33%  { margin-top: -500px; }
60.66% { margin-top: -500px; }
66.66% { margin-top: 0px; }
94.99% { margin-top: 0px; }
  100%  { margin-top: -1000px; }
}

@-webkit-keyframes scrollup {
  0%   { margin-top: 0; }
27.33%  { margin-top: 0 }
  33.33%  { margin-top: -500px; }
60.66% { margin-top: -500px; }
66.66% { margin-top: -1000px; }
94.99% { margin-top: -1000px; }
  100%  { margin-top: 0 }
}
@-moz-keyframes scrollup {
  0%   { margin-top: 0; }
27.33%  { margin-top: 0 }
  33.33%  { margin-top: -500px; }
60.66% { margin-top: -500px; }
66.66% { margin-top: -1000px; }
94.99% { margin-top: -1000px; }
  100%  { margin-top: 0 }
}
@-ms-keyframes scrollup {
  0%   { margin-top: 0; }
27.33%  { margin-top: 0 }
  33.33%  { margin-top: -500px; }
60.66% { margin-top: -500px;...