CSS在列表元素中对齐子画面

Question

我有这个列表菜单，我想要显示每个项目的箭头，这样当你将鼠标悬停在项目上时，箭头就会改变颜色。到目前为止，我的问题似乎是将这个箭头垂直居中对齐。正如你从屏幕截图中看到的，它有点不对劲。忽略箭头和超链接之间缺少的空格。

小提琴：http://jsfiddle.net/7xbse/

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HTML，

<li ><a class="clear-block" href="http://wordpress.local/archives/category/announcements" title="View all posts filed under Announcements">
 <span class="tt">Announcements <strong>(1)</strong></span>
 <span class="c1"></span>
</a></li>
<li ><a class="clear-block" href="http://wordpress.local/archives/category/c-sharp" title="View all posts filed under C#">
 <span class="tt">C# <strong>(1)</strong></span>
 <span class="c1"></span>
</a></li>
<li  class="extends"><a class="clear-block" href="http://wordpress.local/archives/category/c-plus-plus" title="View all posts filed under C++">
 <span class="tt">C++ <strong>(1)</strong></span>
 <span class="c1"></span>
</a>
   <ul class="sub-menu">
    <li ><a class="clear-block" href="http://wordpress.local/archives/category/c-plus-plus/multiplexing-io" title="View all posts filed under Multiplexing I/O">
 <span class="tt">Multiplexing I/O <strong>(1)</strong></span>
 <span class="c1"></span>
</a></li>
   </ul>
</li>

CSS，

.block ul.menu, .block ul.menu ul, .block ul.menu li, .block .box, .block .box .entry{
  margin:0;
  padding:0;
  list-style-type:none;
  line-height: normal;
}

.block ul.menu li, .block ul.box .entry{
  border-bottom:1px dotted #aaa;
  border-top:1px dotted #fff;
}

/* no border on 1st list item */
.block ul.menu li.first,
.block ul.menu li:first-child,
.block ul.box .entry.first,
.block ul.box .entry:first-child{border-top:0 !important;}

.block ul.menu li.last,
.block ul.menu li:last-child,
.block ul.box .entry.last,
.block ul.box .entry:last-child{border-bottom:0 !important;}

.block ul.menu li .expand{display: none;}

.block ul.menu li, .block ul.box .entry {
  position: relative;
  z-index: 5;
}

.block ul.menu li a {
  background:transparent url(../images/icons_old.png) no-repeat 4px -816px;
}

/* titles */
.block ul.menu .tt {
  display:block;
}

.block ul.menu a:hover .tt{
  text-decoration:underline;
}

/* content - primary */
.block ul.menu .c1{
  display:block;
  line-height: 150%;
  color:#333;
  text-decoration:none;
}

/* information block (left side) */
.block ul.menu .base {
  overflow:hidden;
  display:block;
}

Answer 1

这是一个没有考虑菜单行高度的精灵图像的例子。所以箭头没有对齐。诀窍就是修好精灵。

Answer 2

与其使用巨大的CSS精灵，为什么不单独保存每个图像，并利用background-position: 0 50%将图像垂直居中的事实？