Cascade Style Sheets

Cascade Style Sheets (CSS)

Cascade Style Sheets

A CSS is made up of two parts: the selector and declaration. The selector states which tag the rule applies. The declaration stats what happens when the rule is applied.

The declaration is made up of two elements: a property and value. A declaration must end with a semicolon.

Multiple declarations can be contained in a single rule.

Multiple selectors can be contained in a single rule. A comma must be used after each selector except the last.

h1, h2, h3 {color:red; font-weight:bold;}

Multiple rules can be applied to the same selector.

h1, h2, h3 {color:red; font-weight:bold;}

h3 {font-style:italic;}

Contextual Selectors

Contextual selectors use more than one tag in the selector. The tag closest to the declaration is the targeted tag. The additional tag(s) state where the target tag must be located in the markup up in order for target tag to be affected. Contextual selectors have spaces between them.

Contextual selector examples

<html>
<head>
	<title>Contextual Selector Example 1</title>
	<link href="style_sheets/contextual_selector_example_1.css" rel="stylesheet" type="text/css">
</head>
<body>

<h1>Contextual selectors are <em>very</em> selective.</h1>

<p>This example shows how to target a <em>specific</em> tag using the document hierarchy.</p>

<p>Tags only need to be descendants <span>in the <em>order stated</em> in the selector</span>; other tag can be in between and the selector still works.</p>
</body>
</html>

NOTE: The only difference between example html sheets is the style sheet that links them which is noted below for convenience.

em { color:red }

Contextual example 1

p em {color:red }

Contextual example 2

p span em {color:red}

Contextual example 3

Adding Classes & IDs

Adding classes & IDs to the tags in XHTML enables you to style without regard to document hierarchy.

Simple use of a class p42.

CSS contents:

p { font-family: Helvetica, sans-serif; }
.specialtext {font-weight:bold; }

Simple Use Example

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Cascade Style Sheets

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