harder to identify the shape of a word if every letter is nearly the same height. For the same reason, some sign manuals discourage all-capitals text. Use in web design In computing one use of x-height is as a unit of measurement in web pages. In CSS and LaTeX the x-height is called an ex. The use of ex in dimensioning objects, however, is less stable than use of the em across browsers. Internet Explorer, for example, dimensions ex at exactly one half of em, whereas Mozilla Firefox dimensions ex closer to the actual x-height of the font, rounded relative to the font's current pixel height. Thus, the exact ratio of ex to em can vary by font size within a browser if the determined values are rounded to the nearest whole unit. For example, a browser calculating an x-height of 45% on a font 10 pixels tall may round ex to either 4 pixels or 5 pixels or leave it at 4.5 pixels. Other important dimensions Lowercase letters whose height is greater than the x-height either have descenders which extend below the baseline, such as y, g, q, and p, or have ascenders which extend above the x-height, such as l, k, b, and d. The ratio of the x-height to the body height is one of the major characteristics that defines the appearance of a typeface. The height of the capital letters is referred to as cap height. x-height is most important in regular designs, such as most serif and sans-serif designs; script typefaces that mimic irregular handwriting and calligraphy may not have a consistent x-height across all letters. See also En (typography) Small caps References External links Definition of x-height at typophile.com In the search of ideal line-height Typography