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8.4.3.1. Scaling the line heights

There's an even better way to setline-height, as it turns out, and that's touse a raw number as the value of line-height. Thisis so much better because the number is used as a scaling factor, andit is the factor that is inherited, not the computed value.Let's say you want the line-height of allelements in a document to be one-and-one-half times their

On the other hand, perhaps you wish to make purple any element thatis a descendant of DIV. This would be written:

DIV * {color: purple;}

At first glance, this seems no different than if the* were left out, instead relying on inheritance tocarry the color to all descendants ofDIV. However, there is a very real difference: therule shown would match every DIV descendant, andtherefore override the inheritance mechanism. Thus, even anchorsbackground-position: -150px -100px;}

Figure 6-46

Figure 6-46. Another set of negative lengths

Negative percentages are also possible in theory, although there aretwo issues involved. The first is the limitations of user agents,which may not recognize negative values forbackground-position. The other is that negativepercentages are somewhat interesting to calculate. Figure 6-47 shows why.

Figure 6-47

Figure 6-47. Aligning negative percentage points: two scenarios

This isn't to say that you shouldn't use negative values,

6.2.1.1. Good background practices

An interesting thing about images is that they're laid on top of whatever background color you may have specified. If you're completely tiling GIF, JPEG, or other opaque image types, this doesn't really make a difference, since they'll fill up the document background, leaving nowhere for the color to "peek through," so to speak. However, image formats with an alpha channel, such as PNG, can be partially or