熊猫青春蜜糖迅雷种子:高分跪求一个DW问题！

<td width="28%"><a href="#" onMouseOver="MM_swapImage('a','','img/main_26a.gif','b','','img/main_27b.gif','c','','img/main_28a.gif',1);MM_showHideLayers('Layer1','','show','Layer2','','hide','Layer3','','hide')"><img src="img/main_26a.gif" name="a" width="123" height="35" border="0" id="a"></a></td>
<td width="16%"><a href="#" onMouseOver="MM_swapImage('a','','img/main_26b.gif','b','','img/main_27a.gif','c','','img/main_28b.gif',1);MM_showHideLayers('Layer1','','hide','Layer2','','show','Layer3','','hide')"><img src="img/main_27b.gif" name="b" width="70" height="35" border="0" id="b"></a></td>
<td width="16%"><a href="#" onMouseOver="MM_swapImage('a','','img/main_26a.gif','b','','img/main_27b.gif,''c','','img/main_28a.gif',1);MM_showHideLayers('Layer1','','hide','Layer2','','hide','Layer3','','show')"><img src="img/main_28a.gif" name="c" width="70" height="35" border="0" id="c"></a></td>

当鼠标滑过第三个图片时候没有变化，请问是哪里的问题啊？