Difference between revisions of "Cascade Style Sheets"

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== Selectors ==
== Selectors ==


=== Contextual Selectors ===
[[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 ==


Three ways to add styles to your pages.
[[Adding Styles to Web pages]]
 
==== Inline ====
 
Add to a tag using <code>style</code> attribute
 
<pre><p style="enter CSS"></p></pre>
 
==== Embedded ====
 
Add styles in the <code>head</code> of XHTML document


<pre><style type="text/css">enter CSS</style></pre>
== Psuedo Elements and Classes ==


==== Linked ====
[[Psuedo Elements and Classes]]


Style is in another document and the markup is linked to the style.
== Cascade and Rule Declarations ==


<pre><link href="style_sheet.css" media="screen" rel="stylesheet" type="text/CSS" /></pre>
[[Cascade and Rule Declarations]]


== Pseudo Classes ==
== Styling Fonts and Text ==


Classes that cause rules to be applied when a specific event happens. These classes are not attached to tags in  markup. p50
[[Styling Fonts and Text]]


=== Anchor Link Pseudo Classes ===
== Positioning Elements aka ''The Box'' ==


Commonly used with hyperlinks. p50
[[Positioning Elements]]


Link
== Basic Page Layout ==
Visited
Hover
Active


=== Other Useful Pseudo-Classes ===
[[Basic Page Layout]]


This rule selects the first-child element with the name x.
== Tips creating styles ==
<pre>x:first-child</pre>


 
To eliminate the difference between user agents always zero out margins and padding on all elements.
This rule selects the focus of the user with the name x.
<pre>x:focus</pre>
 
== 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.
<pre>x:first-letter</pre>
 
This rule selects the first line of tag name x and applies your style.
<pre>x:first-line</pre>
 
This rule adds specified text before an element of tag name x.
<pre>x:before</pre>
 
This rule adds specified text after an element of tag name x.
<pre>x:after</pre>
 
Example of x:before and x:after
 
<pre>h1.age:before {content:"Age:"}
h1.age:after {content:"years old."}
 
Code <h1 class="age">36</h1> displays "Age: 36 years old."</pre>
 
== Cascade ==
 
Styles passing from higher to lower hierarchy levels.
 
=== Cascade Rules ===
 
Cascade Rules p57:
# Find all declarations that apply to each element and property
# Sort by order and weight
# Sort by specificity
# Sort by order
 
==== Weight of declaration ====
 
Define a rule as important using the exclamation point. Marking a tag as important will override the cascade.
 
<pre>p {color:red !important; font-size:12pt;}</pre>
 
== Rule Declarations ==
 
Declarations are made up of a property and value.


Example:
Example:
<pre>p {color:red;}</pre>
<pre>* {margin:0; padding:0;}</pre>
 
color = property and red = value
 
Values fall into three main types:
# Words
# Numerical values
# Color values
 
=== Numerical values ===


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


Two main groups of numerical values:
[http://www.w3.org/Style/CSS/ Cascading Style Sheets home page]
# Absolute
# Relative


Absolute value describes a real distance.
[http://www.w3.org/Style/CSS/current-work Cascading Style Sheets Current Work]
Relative value compared to another.


Absolute value chart:
[http://www.w3.org/TR/CSS21/ Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification]


{| border="1" cellspacing="0" cellpadding="5" align="center"
[http://www.w3.org/TR/REC-CSS2/ Cascading Style Sheets, level 2 CSS2 Specification]
! Absolute Value
! Unit Abbreviation
|-  
| Inches
| in
|-
| Centimeters
| cm
|-
| Millimeters
| mm
|-
| Points
| pt
|-
| Picas
| pc
|-
| Pixels
| px
|}


Relative value chart:
[http://www.w3.org/TR/REC-CSS1 Cascading Style Sheets, level 1 CSS1 Specification]


{| border="1" cellspacing="0" cellpadding="5" align="center"
[http://www.cssmenumaker.com/ CSS Menu Maker]
! 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 ===
== Interesting CSS resources ==


Hexadecimal format
[https://svgontheweb.com/ SVG on the Web] A Practical Guide


<pre>#RRGGBB</pre>
[https://web-design-weekly.com/2014/11/18/viewport-units-vw-vh-vmin-vmax/ Viewport Units vm vh vmin vmax]


Percentages format
[https://medium.com/@aniboaz/animate-svg-4fa7dd00e860 Animate SVGs with CSS] blog led me to [https://jonsuh.com/blog/animate-svg-with-css/ Animate SVG with CSS]


<pre>R%, G%, B% </pre>


<center>[[web development|Back to Web Development]]</center>
<center>[[web development|Back to Web Development]]</center>

Latest revision as of 17:54, 22 September 2018

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

Selectors

Adding Styles to Web pages

Adding Styles to Web pages

Psuedo Elements and Classes

Psuedo Elements and Classes

Cascade and Rule Declarations

Cascade and Rule Declarations

Styling Fonts and Text

Styling Fonts and Text

Positioning Elements aka The Box

Positioning Elements

Basic Page Layout

Basic Page Layout

Tips creating styles

To eliminate the difference between user agents always zero out margins and padding on all elements.

Example: 

* {margin:0; padding:0;}

Helpful links

Cascading Style Sheets home page

Cascading Style Sheets Current Work

Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification

Cascading Style Sheets, level 2 CSS2 Specification

Cascading Style Sheets, level 1 CSS1 Specification

CSS Menu Maker

Interesting CSS resources

SVG on the Web A Practical Guide

Viewport Units vm vh vmin vmax

Animate SVGs with CSS blog led me to Animate SVG with CSS


Back to Web Development
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