CSS

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The information is obtained from w3schools.com.

To quickly test CSS code, go to online html editor website to try eg squarefree.com.

CSS

Syntax

p
{
color:red;
text-align:center;
}

where p is called selector and anything inside {} is declarations with a format of property:value.

Comments

A CSS comment starts with /* and ends with */. Comments can also span multiple lines

Selectors

https://www.w3schools.com/cssref/css_selectors.asp

selector HTML css
element selector <p>Every paragraph will be affected by the style.</p> p { text-align:center;color:red; }
id selector <p id="para1">Hello World!</p> #para1 { text-align:center;color:red; }
class selector <p class="center">Red and center-aligned paragraph.</p> .center { text-align:center;color:red; }
p.center { text-align:center;color:red; }

"element" selector

p {  text-align:center;color:red; }

The html example is 

<p>Every paragraph will be affected by the style.</p>

Default CSS Values for HTML Elements

id selector

id selector is for one instance. 

#para1  { text-align:center;color:red; }

The html example is 

<p id="para1">Hello World!</p>

class selector, "element.class" selector

https://www.w3schools.com/cssref/sel_class.asp 

.center { text-align:center;color:red; }

You can also specify that only specific HTML elements should be affected by a class. 

p.center { text-align:center;color:red; }

The html example is 

<h1 class="center">Red and center-aligned heading</h1>
<p class="center">Red and center-aligned paragraph.</p>

Real example in Chapter 9 <Style3Column.htm> of Creating a Website. The CSS has 

.Header {
  text-align: center;
  background-color: rgb(210,210,210);
  color: white;
}
.LeftPanel {
  position: absolute;
  top: 75px;
  left: 10px;
  width: 150px;
  background-color:#eee;
  border-width: 1px;
  border-style: solid;
  border-color: black;
  padding-bottom: 8px;
}
.RightPanel {
  position: absolute;
  top: 75px;
  right: 10px;
  width: 150px;
  background-color:#eee;
  border-width: 1px;
  border-style: solid;
  border-color: black;
  padding-bottom: 8px;
}
.CenterPanel {
  margin-left: 161px;
  margin-right: 161px;
}

The Html has 

<body>
<div class="Header"> ... </div>
<div class="LeftPanel"> ... </div>
<div class="RightPanel"> ... </div>
<div class="CenterPanel"> ... </div>
<div class="Class1 Class2"> ... </div>
</body>

group selectors

h1,h2,p { text-align:center;color:red; }

The html example is 

<h1>Hello World!</h1>
<h2>Smaller heading!</h2>
<p>This is a paragraph.</p>

Three ways to insert CSS

External style sheet: link tag

HTML: link tag, How to Create Printer-friendly Pages with CSS. 

<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>

Internal style sheet

<head>
<style>
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/background.gif");}
</style>
</head>

Inline style sheet

<p style="color:sienna;margin-left:20px;">This is a paragraph.</p>

Cascading order (last one has the highest priority)

  1. Browser default
  2. External style sheet
  3. Internal style sheet (in the head section)
  4. Inline style (inside an HTML element)

Box Model

Border

We can create border for a paragraph or an image (CSS [attribute~=value] Selector).

Padding

Space between texts and border box. 

padding-top:25px;
padding-bottom:25px;
padding-right:50px;
padding-left:50px;

Background color/image

How to Change the Background Color With CSS 

body {background-color:#b0c4de;}
body {background-image:url("paper.gif");}
body {background:#ffffff url("img_tree.png") no-repeat right top;}

A simple example is this page.

Text

Color, alignment, decoration and indentation, fonts, styles 

body {color:red;}
h1 {color:#00ff00;}
p.ex {color:rgb(0,0,255);}

h1 {text-align:center;}
p.date {text-align:right;}
p.main {text-align:justify;}

a {text-decoration:none;}
h2 {text-decoration:line-through;}
h3 {text-decoration:underline;}

p {text-indent:50px;}

p.serif{font-family:"Times New Roman",Times,serif;}
p.sansserif{font-family:Arial,Helvetica,sans-serif;}

p.normal {font-style:normal;}
p.italic {font-style:italic;}
p.oblique {font-style:oblique;}

CSS font size

Links

https://www.w3schools.com/Css/css_link.asp 

a:link {color:#FF0000;}    /* unvisited link */
a:visited {color:#00FF00;} /* visited link */
a:hover {color:#FF00FF;}   /* mouse over link */

Lists

ul.a {list-style-type:circle;}
ul.b {list-style-type:square;}
ol.c {list-style-type:upper-roman;}
ol.d {list-style-type:lower-alpha;}

Tables

table, td, th 
{
border:1px solid green;
}
th
{
background-color:green;
color:white;
}

See here for a link to create a fancy table.

Dimension (Width and height)

img.normal  { height:auto; }
img.big { height:120px; }
p.ex { height:100px; width:100px; }

Positioning

http://www.w3schools.com/css/css_positioning.asp How to show overflow in an element using scroll]

Float

  • An image with a caption that floats to the right
  • the example of creating a horizontal menu
  • the example of creating a homepage without tables (partition of a webpage)

Horizontal Align

Tips:

  1. Use percent (%) instead of pixels (px).
  2. Use margin:auto
.center
{
  margin:auto;
  width:70%;
  background-color:#b0e0e6;
}

Pseudo-elements

The ::first-line pseudo-element is used to add a special style to the first line of a text.

Navigation Bar

li { float:left; }
a { display:block; width:60px; }

Image gallery

Image Opacity/Transparency

  • Creating transparent images - Hover effect
  • Creating a transparent box with text on a background image
  • Text in Transparent Box

Image Sprites

An image sprite is a collection of images put into a single image.

A web page with many images can take a long time to load and generates multiple server requests.

Using image sprites will reduce the number of server requests and save bandwidth.

Sprite editor

All Examples

http://www.w3schools.com/css/css_examples.asp

30 Seconds of CSS

mentioned in this article

Printing

Using CSS to Format Documents for Printing

CSS3

Box

  • Shadow
  • Rounded corners

2D transform

Transition

Animation

Multiple columns

Check out the last example

Free framework

9 open source CSS frameworks for frontend web development

simplecss

Simple.css {}

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