In HTML IDs must be unique, use class instead like
<ul id="products" style="list-style:none;">
$for item in data.response["Galleries"]:
<li style="float:left" class="photoLink">
<a href="$item['PhotoUrl']">
<img src=$item["PhotoUrl"] alt="加载失败" style="max-width:75px;max-height:75px" title="点击查看大图"/>
</a>
<div class="img_menu" style="height:20px;width:75px;background-color:black;opacity:0.5"/>
</li>
</ul>
jQuery
<script type="text/javascript">
$$(document).ready(function(){
$$(".photoLink").mouseenter(function(){
$$(this).find(".img_menu").css("margin-top","-20px");
});
$$(".photoLink").mouseleave(function(){
$$(this).find(".img_menu").css("margin-top","0px");
});
});
</script>
Additionally You can use .hover()
<script type="text/javascript">
$$(document).ready(function(){
$$(".photoLink").hover(function(){
$$(this).find(".img_menu").css("margin-top","-20px");
}, function(){
$$(this).find(".img_menu").css("margin-top","0px");
});
});
</script>