Web Design in a Nutshell, 3rd Edition

Font weight can be specified either as a descriptive term (normal, bold, bolder, lighter) or as one of the nine numeric values listed above. The default font weight is normal, which corresponds to 400 on the numeric scale. Typical bold text corresponds to 700 on the numeric scale. There may not be a font face within a family that corresponds to each of the nine levels of boldness (some may come in only normal and bold weights). Figure 18-6 shows the effect of each of the values on the popular Verdana web font face in the Firefox browser (note that bold kicks in at 600, not 700).

It is evident that the numeric font-weight values are not useful when multiple weights are not available for the font. There’s no harm in using them, but don’t expect them to change the weights of an existing font. It merely looks for font weights that are already available.

Figure 18-6. The effect of font-weight values

Unfortunately, the current browsers are inconsistent in support of the font-weight property, mainly due to the lack of available fonts that fit the criteria. The values that are intended to make text lighter than normal weight are particularly unsuccessful. Of the possible values, only bold and bolder will render reliably as bold text. Most developers stick to those values and ignore the rest.