absolute unit A unit of measurement that is fixed in size regardless of the device rendering the Web page.

child element An element contained within a parent element.

color name A CSS name for a commonly-used color.

color value A numeric expression that describes the properties of a color.

contextual selector A select that matches elements based on their positions in the document hierarchy.

CSS @rule A rule that specifies a command or directive that controls how browsers interpret and run the contents of a CSS style sheet.

CSS1 The first version of CSS, introduced in 1996.

CSS2 The second version of CSS, introduced in 1998.

CSS2.1 A version of CSS introduced in 2002 to clean up minor errors in the original introduction of CSS2.

CSS3 The current working draft version of CSS.

density The number of dots per inch in an output device.

descendant element An element that descends from a parent element.

em unit A unit of measurement that expresses the font size relative to the font size of the parent element.

embedded style sheet A style sheet placed within the head section of an HTML file.

external style sheet A style sheet placed in an external file.

font A text typeface.

generic font A font name that describes the general appearance of a font.

hanging indent A negative text indentation in which the first line extends to the left of the text block.

hexadecimal A number expressed in the base 16 numbering system.

HSL model A color model in which colors are selected from a color wheel at varying levels of saturation and lightness.

hue The tint of a color based on the color's location on the color wheel.

id attribute A Web form control attribute that identifies the control box.

initial cap An effect in which the first letter of the first line of a text block appears larger than the surrounding text.

inline style A style created using the style attribute within an HTML file.

kerning The space between letters.

leading The height of a text line.

lightness The brightness of a color ranging from 0% (black) up to 100% (white).

parent element An element that contains one or more other elements.

progressive enhancement A coding technique in which code conforming to older standards is placed before newer code.

pseudo-class A classification of an element based on its current status, position, or use in the document.

pseudo-element An element that does not exist in the document hierarchy, but rather is based on objects that exist in the rendered Web page.

relative unit A unit of measurement that is expressed relative to the sizes of other objects within the Web page.

resolution The size of the output device, typically expressed in pixels.

RGB model A color model in which colors are defined by varying intensities of red, blue, and green.

RGB triplet A set of numbers representing intensities of red, green, and blue.

saturation The intensity of a color ranging from 0% (no color) up to 100% (full color).

scalable A page that can be rendered the same way no matter what size is used by the browser.

selector The part of the style rule that defines what element or elements are affected by the rule.

sibling element Two elements that share a common parent element.

specific font A font name that references a font installed on the user's computer.

style inheritance A process in which style properties are passed from a parent element to its children.

style rule A list of style properties applied to an element or to a group of elements.

tracking The space between words.

Web font A font that is downloadable by the browser to be used in rendering the Web page.

Web Font Service Bureau A service that supplies Web fonts that page designers can link to for a fee.

Web safe font A font that is displayed in mostly the same way in all browsers and on all devices.

wildcard selector The asterisk selector (*) which selects all elements in a document.