scrollTop和offsetTop的区别

Question

/**
这个是我转司徒正美的一个图片上下无缝滚动的效果
**/
<style type="text/css">
    #marquee {
        position: relative;
        height: 300px;
        width: 200px;
        overflow: hidden;
        border: 10px solid #369;
        padding:0;
        margin:0;
    }
    #marquee img {
        display: block;
    }
    #marquee dd {
        margin: 0px;
        padding: 0px;
    }
</style>
<dl id="marquee">
    <dt>
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s017.jpg" alt="无缝滚动" />
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s018.jpg" alt="无缝滚动" />
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s019.jpg" alt="无缝滚动" />
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s020.jpg" alt="无缝滚动" />
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s021.jpg" alt="无缝滚动" />
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s022.jpg" alt="无缝滚动" />
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/o_s023.jpg" alt="无缝滚动" />
    </dt>
    <dd>
    </dd>
</dl>
<script type="text/javascript">
    var Marquee = function (id) {
        var container = document.getElementById(id),
  original = container.getElementsByTagName("dt")[0],
  clone = container.getElementsByTagName("dd")[0],
  speed = arguments[1] || 10;
        clone.innerHTML = original.innerHTML;

        alert(container.scrollTop);
        var rolling = function () {
            if (container.scrollTop == clone.offsetTop) {//我现在纠结的就是container.scrollTop和clone.offsetTop的区别
                                                           为什么clone.offsetTop是1050，而外面的container.scrollTop却是0    

                container.scrollTop = 0;
            } else {
                container.scrollTop++;
            }
        }
        var timer = setInterval(rolling, speed)
        container.onmouseover = function () { clearInterval(timer) }
        container.onmouseout = function () { timer = setInterval(rolling, speed) }
    }
    window.onload = function () {
        Marquee("marquee");
    }
</script>

Answer 1

这个我看了，但测试起来还是很抽象，有没有具体点的