偷偷问个问题，，，，
<div id=block3 >
<IMG alt= "播放节点 " src= "1.gif ">
</div>

怎样重设 src= "2.gif "啊？

[解决办法]
<div id=block3 >
<img id= "wc_0 " alt= "播放节点 " src= "1.gif " alt= " ">
</div>
<button onclick= "document.getElementById( 'wc_0 ').src = '2.gif ' "> 换 </button>