4. Measurements, URLs, and Color Units

In the discussion of CSS syntax in Chapter 1, you saw that the second part of each CSS declaration is a value. In this chapter, you’ll explore some common units for defining sizes (<length> and <percentage>), colors (<color>), and URLs (<url>) for defining these values.


Dimensions and other measurements, such as font-size, are not just raw numbers but a number of some specified of units of measure. CSS has quite a variety of measurement units; the most commonly used are outlined in the following sections.

Pixels (px)


A pixel unit (<length>) is a fixed measurement based on the size of a common ...

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