http://quirks.spec.whatwg.org/#the-line-height-calculation-quirk

[[
In quirks mode and almost standards mode, an inline box that matches the following conditions, must, for the purpose of line height calculation, act as if the box had a height of zero.
]]

On Fri, 23 Nov 2012 03:21:39 +0100, Kang-Hao (Kenny) Lu <kanghaol@oupeng.com> wrote:
> I think you meant to say "the box had a 'line-height' of zero" instead,
> as the content height of an inline box never affects the line height,
> the "line-height box" does. This is what CSS 2.1 10.8 says
>
>   # The height of each inline-level box in the line box is calculated.
>   # For replaced elements, inline-block elements, and inline-table
>   # elements, this is the height of their margin box; for inline boxes,
>   # this is their 'line-height'. (See "Calculating heights and margins"
>   # and the height of inline boxes in "Leading and half-leading".)
>
> (What 'window.getComputedStyle' would return for 'height' is sort of a
> parallel, although also interesting, question.)