Vertical alignment text in container WebKit vs Firefox

The problem is that Firefox and WebKit based browsers seem to align text vertical in different way when contained in a element that have a even height/line-height and the font-size is uneven (or vice versa). I have looked at some similar thread, but I haven't really seen any great explanation for my question.

Consider http://alternativeto.net/test2.htm. This is a really simple page with just

    .box
    {
        font-size: 15px;
        font-family: Helvetica, Arial;
        background-color: Blue;
        height: 20px;
        width: 60px;
        color: White;
        line-height: 20px;
    }

And

    

        A text.
    

If you open that page up in Chrome and Firefox you notice that they align the texts in different ways: http://screencast.com/t/tjgA2d7T

Is there any way to fix this? Is there any "text-align" property or something that I missed?