IT online Exam

IT online Exam

Sunday, 23 July 2017

Lesson No. 1 Web Publishing - CSS



What is CSS?
  • CSS stands for Cascading Style Sheets
  • CSS describes how HTML elements are to be displayed on screen, paper, or in other media
  • CSS saves a lot of work. It can control the layout of multiple web pages all at once
  • CSS is used to define styles for your web pages, including the design, layout and variations in display for different devices and screen sizes. 
  • External stylesheets are stored in CSS files


CSS Syntax

A CSS rule-set consists of a selector and a declaration block:
CSS rule syntax


  • The selector points to the HTML element you want to style.
  • The declaration block contains one or more declarations separated by semicolons.
  • Each declaration includes a CSS property name and a value, separated by a colon.
  • A CSS declaration always ends with a semicolon, and declaration blocks are surrounded by curly braces.

Example:
p {
    color: red;
    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



1.  External Style Sheet

With an external style sheet, you can change the look of an entire website by changing just one file!
Each page must include a reference to the external style sheet file inside the <link> element. The <link> element goes inside the <head> section:
An external style sheet can be written in any text editor. The file should not contain any html tags. The style sheet file must be saved with a .css extension.
Example:
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>

Here is how the "myStyle.css" looks:
body {
    background-color: lightblue;
}

h1 {
    color: navy;
    margin-left: 20px;
}


Note: 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;


2.  Internal Style Sheet

An internal style sheet may be used if one single page has a unique style.
Internal styles are defined within the <style> element, inside the <head> section of an HTML page:
Example:
<head>
        <style>
        body {
                background-color: linen;
        }

        h1 {
                color: maroon;
                margin-left: 40px;
        }
        </style>
</head>

3.  Inline Styles

An inline style may be used to apply a unique style for a single element.
To use inline styles, add the style attribute to the relevant element. The style attribute can contain any CSS property.
The example below shows how to change the color and the left margin of a <h1> element:
Example:
<h1 style="color:blue;margin-left:30px;">This is a heading.</h1>

Note: If some properties have been defined for the same selector (element) in different style sheets, the value from the last read style sheet will be used. 
 



CSS Selectors

CSS selectors are used to "find" (or select) HTML elements based on their element name, id, class, attribute, and more.

The element Selector

The element selector selects elements based on the element name.
Example:

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

The id Selector

·         The id selector uses the id attribute of an HTML element to select a specific element.
·         The id of an element should be unique within a page, so the id selector is used to select one unique element!
·         To select an element with a specific id, write a hash (#) character, followed by the id of the element.
Example:
#para1 {
    text-align: center;
    color: red;
}
<p id="para1">                            
   .....................................................
    ...................................................
</p>

 

The class Selector

·         The class selector selects elements with a specific class attribute.
·         To select elements with a specific class, write a period (.) character, followed by the name of the class.

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

Grouping Selectors

If you have elements with the same style definitions, it will be better to group the selectors, to minimize the code.
To group selectors, separate each selector with a comma.
Example:
h1, h2, p {
    text-align: center;
    color: red;
}

Important CSS properties
Color - The color property specifies the color of text.
Example:
body {
  color: red;
}

h1 {
  color: #00ff00;
}

Background-image - The background-image property sets one or more background images for an element. By default, a background-image is placed at the top-left corner of an element, and repeated both vertically and horizontally.
Example:

body {
  background-image: url("img_tree.gif"), url("paper.gif");
  background-color: #cccccc;
}

Background-color - Set the background color for a page:
Example:

body {background-color: coral;}

Background - Set different background properties in one declaration for background color, image, position, size, attachment, etc.
Example:

body {
  background: lightblue url("img_tree.gif") no-repeat fixed center;
}

Border - The border property is a shorthand property for:

Example:

h1 {
  border: 5px solid red;
}

h2 {
  border: 4px dotted blue;
}

Text-align - The text-align property specifies the horizontal alignment of text in an element.
Values are   left|right|center|justify|initial|inherit;
Example:

div {
  text-align: center;
}

Text-decoration - The text-decoration property specifies the decoration added to text, and is a shorthand property for:
  • text-decoration-line (required)
  • text-decoration-color
  • text-decoration-style

Example:

h1 {
  text-decoration: overline;
}

h2 {
  text-decoration: line-through;
}

h3 {
  text-decoration: underline;
}

h4 {
  text-decoration: underline overline;
}

Font - The font property is a shorthand property for:
The font-size and font-family values are required. If one of the other values is missing, their default value are used.
Example:

p {
  font: italic bold 12px/30px Georgia, serif;
}

Font-size - The font-size property sets the size of a font.
div {
  font-size: 15px;
}

Font-family - The font-family property specifies the font for an element.
The font-family property can hold several font names as a "fallback" system. If the browser does not support the first font, it tries the next font.
Example:

H2 {
  font-family: "Times New Roman", Times, serif;
}

Font-style - The font-style property specifies the font style for a text. Values are normal|italic|oblique|initial|inherit
Example:

p {
  font-style: italic;
}

font-weight - The font-weight property sets how thick or thin characters in text should be displayed.
The values are - normal|bold|bolder|lighter|number|initial|inherit;
Example:

p {
  font-weight: bold;
}

letter-spacing - The letter-spacing property increases or decreases the space between characters in a text. The values are normal|length|initial|inherit;
Example:

h2 {
  letter-spacing: 2px;
}


Float - The float property specifies how an element should float.
Example:

img  {
  float: right;
}

Margin - The margin property sets the margins for an element, and is a shorthand property for the following properties:

Example:

p {
  margin: 35px;
}
p {
     margin: 10px 5px 15px 20px;
}

Padding - An element's padding is the space between its content and its border.
The padding property is a shorthand property for:
·         Example:

Example:

p {
  padding: 35px;
}

z-index - The z-index property specifies the stack order of an element.
An element with greater stack order is always in front of an element with a lower stack order.
Example:

img {
  position: absolute;
  left: 0px;
  top: 0px;
  z-index: -1;
}

Position - The position property specifies the type of positioning method used for an element (static, relative, absolute, fixed, or sticky).
Example:

 h2 {
  position: absolute;
  left: 100px;
  top: 150px;
}

Value
Description
static
Default value. Elements render in order, as they appear in the document flow
absolute
The element is positioned relative to its first positioned (not static) ancestor element
fixed
The element is positioned relative to the browser window
relative
The element is positioned relative to its normal position, so "left:20px" adds 20 pixels to the element's LEFT position
sticky
The element is positioned based on the user's scroll position
A sticky element toggles between relative and fixed, depending on the scroll position. It is positioned relative until a given offset position is met in the viewport - then it "sticks" in place (like position:fixed).
Note: Not supported in IE/Edge 15 or earlier. Supported in Safari from version 6.1 with a -webkit- prefix.
initial
Sets this property to its default value. 
inherit
Inherits this property from its parent element.






Top - The top property affects the vertical position of a positioned element. This property has no effect on non-positioned elements.
Example:

 div {
  position: absolute;
  top: 50px;
  border: 3px solid green;
}

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3 comments:

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  2. akshay26 July 2017 at 08:03

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  3. Unknown7 March 2019 at 02:15

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