Difference between revisions of "Cascade Style Sheets"

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h3 {font-style:italic;}</pre>
h3 {font-style:italic;}</pre>


== Selectors ==
[[Selectors]]
 
=== 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.
 
Example: The p is targeted tag. Only p tags within div tags will be red.
<pre>div p {color:red;}</pre>
 
 
==== Contextual selector examples ====
<pre><html>
<head>
<title>Contextual Selector Example 1</title>
<link href="style_sheets/contextual_selector_example_1.css" rel="stylesheet" type="text/css">
</head>
<body>
</pre>
 
==== Child selectors ====
 
Write a rule so the target tag has to be a child of a specific tag.
 
<pre>p>em {color:green;}</pre>
 
 
==== Contextual Class Selectors ====
 
You can combine tag and class name to make a selector more specific.
 
The second line states '''any tags with "specialtext" class will be bold'''.
 
The third line states '''"specialtext" class must be within the context of p tag for rule to apply'''.
 
<pre>
p { font-family: Helvetica, sans-serif; }
.specialtext { font-weight:bold; }
p.specialtext { color:red}
</pre>
 
[http://www.gotopinion.info/styles/class_selector_example_0.html | Class Selector Example 0]
 
You can further specify by adding more tags.
 
The fourth line states '''span tag within a paragraph with "specialtext" class will be italicized'''
 
<pre>
p { font-family: Helvetica, sans-serif; }
.specialtext { font-weight:bold; }
p.specialtext { color:red}
p.specialtext span { font-style:italic; }
</pre>
 
[http://www.gotopinion.info/styles/class_selector_example_1.html | Class Selector Example 1]
 
==== Skipping the restrictions of hierarchy ====
The line states '''span tag can be a descendant of any tag with specialtext class'''
<pre>.specialtext span { color:blue; }
</pre>
 
=== IDs ===
 
ID synax is similar to classes except a hash (#) symbol is used versus a class's period.
 
==== Difference between Classes & IDs ====
 
The ID can only be used once per page and a class may appear many times.
 
If you want to identify a unique piece of your page's markup use an ID.
 
If you want to apply rules to multiple tags in same page or many pages use a class.
 
=== Universal Selector ===
 
The asterisk (*) means anything so this rule means all text will be blue.
<pre>* { color:blue; }
</pre>
 
Another use is as the inverse of a child selector. This rule means any em tag that is at least a grandchild of the p tag, but not a child, is selected.
<pre>p * em { font-weight:bold; }</pre>
 
 
=== Adjacent Sibling Selector ===
 
Rule selects a tag that follows a specific sibling tag. p48
 
=== Attribute Selector ===
 
Attribute selectors use the attributes of the tag. p48


== Adding Styles to Web pages ==
== Adding Styles to Web pages ==

Revision as of 15:53, 19 May 2008

Cascade Style Sheets (CSS)

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;}

Selectors

Adding Styles to Web pages

Three ways to add styles to your pages.

Inline

Add to a tag using style attribute 

<p style="enter CSS"></p>

Embedded

Add styles in the head of XHTML document 

<style type="text/css">enter CSS</style>

Linked

Style is in another document and the markup is linked to the style. 

<link href="style_sheet.css" media="screen" rel="stylesheet" type="text/CSS" />

Pseudo Classes

Classes that cause rules to be applied when a specific event happens. These classes are not attached to tags in markup. p50

Anchor Link Pseudo Classes

Commonly used with hyperlinks. p50

Link Visited Hover Active

Other Useful Pseudo-Classes

This rule selects the first-child element with the name x. 

x:first-child


This rule selects the focus of the user with the name x. 

x:focus

Pseudo-elements

Provides the effect of extra markup without the markup in your code.

This rule selects the first letter of tag name x and applies your style. 

x:first-letter

This rule selects the first line of tag name x and applies your style. 

x:first-line

This rule adds specified text before an element of tag name x. 

x:before

This rule adds specified text after an element of tag name x. 

x:after

Example of x:before and x:after 

h1.age:before {content:"Age:"}
h1.age:after {content:"years old."}

Code <h1 class="age">36</h1> displays "Age: 36 years old."

Cascade

Styles passing from higher to lower hierarchy levels.

Cascade Rules

Cascade Rules p57:

  1. Find all declarations that apply to each element and property
  2. Sort by order and weight
  3. Sort by specificity
  4. Sort by order

Weight of declaration

Define a rule as important using the exclamation point. Marking a tag as important will override the cascade. 

p {color:red !important; font-size:12pt;}

Rule Declarations

Declarations are made up of a property and value.

Example: 

p {color:red;}

color = property and red = value

Values fall into three main types:

  1. Words
  2. Numerical values
  3. Color values

Numerical values

Use to decribe the "distance" or height, width, depth, length, etc. for many values. p61

Two main groups of numerical values:

  1. Absolute
  2. Relative

Absolute value describes a real distance. Relative value compared to another.

Absolute value chart:

Absolute Value Unit Abbreviation
Inches in
Centimeters cm
Millimeters mm
Points pt
Picas pc
Pixels px

Relative value chart:

Relative Value Unit Abbreviation Note
Em em Width of character in a font.
Ex ex Equivalent to the x-height of the given font.
Percentage %

Color Values

Hexadecimal format 

#RRGGBB

Percentages format 

R%, G%, B%

Styling Fonts and Text

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