Relevant to Firefox and Opera in MS Windows…

What's the proper way to center a line of 100px text vertically relative to its line box? The first 3 examples, with line heights of 100, 80 and 10px, are positioned too low. The last example has been 'fudged' with an 80px line height and 16px bottom padding in order to vertically center Arial glyphs in a 100px box.