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258 Learn HTML 4 In a Weekend When setting font measurements, you need to be aware that Windows and the Macintosh platform default to displaying fonts at different dot- pitches (or dots-per-inch, or dpi). Windows defaults to displaying fonts at 96 dpi, whereas the Macintosh defaults to displaying fonts at 72 dpi. This has the effect of causing the default font size to look smaller on a Macintosh than on a Windows system, even if the monitor sizes and screen resolutions are the same. Windows users can change the default dot-pitch for fonts on their systems by clicking the Advanced button in the Display Properties control panel. Many Macintosh browsers have toolbar buttons that can be clicked to increase or decrease the default font size used to display Web pages. Internet Explorer 5 for the Macintosh actually displays fonts using the Windows dot-pitch (96 dpi), but other Macintosh browsers do not. Using Other Measuring Units There are other measuring units, besides pixels and ems, that can be used when setting font sizes. These include: percentages (%), ex-heights (ex), points (pt), picas (pc), inches (in), centimeters (cm), and millimeters (mm). For setting font sizes, percentages work identically to using ems, with a value of 110% being equivalent to 1.1em. Ex-height measurements theoretically should allow setting a font size based on a font's ex-height (the height of a lowercase x). In practice, however, all browsers treat an ex as being exactly half an em, regardless of whether a particular font's ex- height is actually half of its height (which in many cases is not the case). CAUTION Points, picas, inches, and centimeters should never be used when setting font sizes, because they are absolute font sizes that have no meaning since the dimensions of the target media (a Web page) are unknown. They should only be used when creat- ing a style sheet that will only be used when printing a page (by inserting a media="print" attribute in the STYLE element), since the size of the target media (an 8-by-11-inch piece of paper) is known.