web pages more attractive , controlling the design .
The key to understanding how CSS works is to imagine that there is an invisible box around every HTML element.
You can specify any color in CSS in one of three ways:
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rgb values These express colors in terms of how much red, green and blue are used to make it up. For example: rgb(100,100,90)
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hex codes These are six-digit codes that represent the amount of red, green and blue in a color, preceded by a pound or hash #sign. For example: #ee3e80
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color names There are 147 predefined color names that are recognized by browsers.
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DarkCyan We look at these three different ways of specifying colors on the next double-page spread.
CSS treats each HTML element as if it appears in a box, and the background-color property sets the color of the background for that box.
You can specify your choice of background color in the same three ways you can specify foreground colors: RGB values, hex codes, and color names (covered on the next page). If you do not specify a background color, then the background is transparent.
By default, most browser windows have a white background, but browser users can set a background color for their windows, so if you want to be sure that the background is white you can use the background-color property on the elemen
Every color on a computer screen is created by mixing amounts of red, green, and blue. To find the color you want, you can use a color picker.
CSS3 introduces the opacity property which allows you to specify the opacity of an element and any of its child lements. The value is a number between 0.0 and 1.0 (so a value of 0.5 is 50% opacity and 0.15 is 15% opacity).
The CSS3 rgba property allows you to specify a color, just like you would with an RGB value, but adds a fourth value to indicate opacity. This value is known as an alpha value and is a number between 0.0 and 1.0 (so a value of 0.5 is 50% opacity and 0.15 is 15% opacity). The rgba value will only affect the element on which it is applied (not child lements).
hue Hue is the colloquial idea of color. In HSL colors, hue is often represented as a color circle where the angle represents the color, although it may also be shown as a slider with values from 0 to 360.
saturation Saturation is the amount of gray in a color. Saturation is represented as a percentage. 100% is full saturation and 0% is a shade of gray.
lightness Lightness is the amount of white (lightness) or black (darkness) in a color. Lightness is represented as a percentage. 0% lightness is black, 100% lightness is white, and 50% lightness is normal. Lightness is sometimes referred to as luminosity