CSS notes IWP S8CSE ~ Engineering Cracks

CSS

CSS stands for Cascading Style Sheets
Styles define how to display HTML elements
Styles were added to HTML 4.0 to solve a problem
External Style Sheets can save a lot of work
External Style Sheets are stored in CSS files

Styles Solved a Big Problem

HTML was never intended to contain tags for formatting a document.

HTML was intended to define the content of a document, like:

<h1>This is a heading</h1>

<p>This is a paragraph.</p>

When tags like <font>, and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large web sites, where fonts and color information were added to every single page, became a long and expensive process.

To solve this problem, the World Wide Web Consortium (W3C) created CSS.

In HTML 4.0, all formatting could be removed from the HTML document, and stored in a separate CSS file.

All browsers support CSS today.

CSS defines HOW HTML elements are to be displayed. It saves a lot of work.Styles are normally saved in external .css files. External style sheets enable you to change the appearance and layout of all the pages in a Web site, just by editing one single file!

CSS Syntax

A CSS rule has two main parts: a selector, and one or more declarations:

The selector is normally the HTML element you want to style.
Each declaration consists of a property and a value.
The property is the style attribute you want to change. Each property has a value.
A CSS declaration always ends with a semicolon, and declaration groups are surrounded by curly brackets:
Eg: p {color:red;text-align:center;}

CSS Comments

A CSS comment begins with "/", and ends with "/", like this:

/*This is a comment*/
p
{
text-align:center;
/*This is another comment*/
color:black;
font-family:arial;
}

The id and class Selectors

In addition to setting a style for a HTML element, CSS allows you to specify your own selectors called "id" and "class".

The id Selector

The id selector is used to specify a style for a single, unique element.

The id selector uses the id attribute of the HTML element, and is defined with a "#".

The style rule below will be applied to the element with id="para1":

Example

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

The class Selector

The class selector is used to specify a style for a group of elements. Unlike the id selector, the class selector is most often used on several elements.
This allows you to set a particular style for many HTML elements with the same class.
The class selector uses the HTML class attribute, and is defined with a "."
In the example below, all HTML elements with class="center" will be center-aligned:
Efg: .center {text-align:center;}

You can also specify that only specific HTML elements should be affected by a class. In the example below, all p elements with class="center" will be center-aligned:

p.center {text-align:center;}

Three Ways to Insert CSS

There are three ways of inserting a style sheet:

External style sheet
Internal style sheet
Inline style

External Style Sheet

An external style sheet is ideal when the style is applied to many pages. With an external style sheet, you can change the look of an entire Web site by changing one file. Each page must link to the style sheet using the <link> tag. The <link> tag goes inside the head section:

An external style sheet can be written in any text editor. The file should not contain any html tags. Your style sheet should be saved with a .css extension. An example of a style sheet file is shown below:

hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}

Do not add a space between the property value and the unit (such as margin-left:20 px). The correct way is: margin-left:20px

Internal Style Sheet

An internal style sheet should be used when a single document has a unique style. You define internal styles in the head section of an HTML page, by using the <style> tag, like this:

<head>
<style type="text/css">
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
</style>
</head>

Inline Styles

An inline style loses many of the advantages of style sheets by mixing content with presentation. To use inline styles you use the style attribute in the relevant tag. The style attribute can contain any CSS property. The example shows how to change the color and the left margin of a paragraph:

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

a) CSS Background

CSS background properties are used to define the background effects of an element.

CSS properties used for background effects:

background-color
background-image
background-repeat
background-attachment
background-position

Background Color

eg: body {background-color:#b0c4de;}

With CSS, a color is most often specified by:

a HEX value - like "#ff0000"
an RGB value - like "rgb(255,0,0)"
a color name - like "red"

Background Image

The background-image property specifies an image to use as the background of an element. By default, the image is repeated so it covers the entire element. The background image for a page can be set like this: body {background-image:url('paper.gif');}
By default, the background-image property repeats an image both horizontally and vertically. If the image is repeated only horizontally (repeat-x), the background will look better:
body
{
background-image:url('gradient2.png');
background-repeat:repeat-x;
}
Showing the image only once is specified by the background-repeat property:

body
{
background-image:url('img_tree.png');
background-repeat:no-repeat;
}

b) CSS Text

=> Text Color

The color property is used to set the color of the text.
body {color:blue;}
h1 {color:#00ff00;}
h2 {color:rgb(255,0,0);}

ð Text Alignment

The text-align property is used to set the horizontal alignment of a text. Text can be centered, or aligned to the left or right, or justified. When text-align is set to "justify", each line is stretched so that every line has equal width, and the left and right margins are straight (like in magazines and newspapers).

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

ð Text Decoration

The text-decoration property is used to set or remove decorations from text.
The text-decoration property is mostly used to remove underlines from links for design purposes: a {text-decoration:none;}

It can also be used to decorate text:

h1{text-decoration:overline;}
h2{text-decoration:line-through;}
h3{text-decoration:underline;}
h4 {text-decoration:blink;}

ð Text Transformation

The text-transform property is used to specify uppercase and lowercase letters in a text. It can be used to turn everything into uppercase or lowercase letters, or capitalize the first letter of each word.

p.uppercase {text-transform:uppercase;}
p.lowercase {text-transform:lowercase;}
p.capitalize {text-transform:capitalize;}

ð Text-align Property

h1 {text-align:center}
h2 {text-align:left}
h3 {text-align:right}

c) CSS Font

CSS font properties define the font family, boldness, size, and the style of a text.

Difference Between Serif and Sans-serif Fonts

CSS Font Families

In CSS, there are two types of font family names:

generic family - a group of font families with a similar look (like "Serif" or "Monospace")
font family - a specific font family (like "Times New Roman" or "Arial")

Generic family	Font family	Description
Serif	Times New Roman Georgia	Serif fonts have small lines at the ends on some characters
Sans-serif	Arial Verdana	"Sans" means without - these fonts do not have the lines at the ends of characters
Monospace	Courier New Lucida Console	All monospace characters have the same width

Setting font family,style and

p{font-family:"Times New Roman", Times, serif;}

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

h1 {font-size:40px;}
h2 {font-size:30px;}
p {font-size:14px;}

d) CSS Links

Styling Links

Links can be styled with any CSS property (e.g. color, font-family, background, etc.).Special for links are that they can be styled differently depending on what state they are in.

The four links states are:

a:link - a normal, unvisited link
a:visited - a link the user has visited
a:hover - a link when the user mouses over it
a:active - a link the moment it is clicked

a:link {color:#FF0000;} /* unvisited link */
a:visited {color:#00FF00;} /* visited link */
a:hover {color:#FF00FF;} /* mouse over link */
a:active {color:#0000FF;} /* selected link */

Background Color

The background-color property specifies the background color for links:

Example

a:link {background-color:#B2FF99;}
a:visited {background-color:#FFFF85;}
a:hover {background-color:#FF704D;}
a:active {background-color:#FF704D;}

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Friday, June 14, 2013