<input type="text" name=names size=40><br>
<input type="button" value="添加" onclick="this.insertAdjacentHTML('beforeBegin','<input type=text name=names size=40><br>')">
<input type="button" value="添加" onclick="this.insertAdjacentHTML('beforeBegin','<input type=text name=names size=40><br>')">
<input type="text" name=names size=40><br>
</div>
<input type="button" value="添加" onclick="document.getElementById('d').innerHTML+='<input type=text name=names size=40><br>';">
详细见:http://developer.mozilla.org/en/docs/DOM:document.createElement