why does this not vertically center? - image

Question

html code:
<div class="container">
<a class="ank">
<img src="http://www.w3schools.com/images/w3schoolslogoNEW310113.gif" />
</a>
</div>
css code:
.ank
{
display: block;
width: 500px;
height: 500px;
line-height: 100%;
}
img
{
vertical-align: middle;
}
.container
{
display:block;
width: 500px;
height: 500px;
border: 1px solid black;
font-size: 500px;
}
jsfiddle: http://jsfiddle.net/mfBZZ/5/
if i change the jsfiddle, so that anks line-height is 500px, and remove the font-size from container, it works.
but when i add the font-size to container of 500px, and then make the line-height in ank, 100% of that font-size, it doesn't work. it brings the image alittle lower than where it should be.
working jsfiddle: http://jsfiddle.net/eujFY/1/
UPDATE:
this solution works for me:
http://jsfiddle.net/eujFY/2/ <---- updated.

Answer 1

I've seen you found a solution, however it implies setting the height manually on both elements and it requires the usage of unnecessary tags.
So I suggest you to check the "display:table" (container) and "display:table-cell" (inner element) rules: http://jsfiddle.net/RxGS5/
HTML
<div class="container">
<a class="ank">
<img src="http://www.w3schools.com/images/w3schoolslogoNEW310113.gif" />
</a>
</div>
CSS
.container
{
display:table;
width: 500px;
height: 500px;
border: 1px solid black;
}
.ank
{
display: table-cell;
vertical-align: middle;
}