CASCADING
STYLE SHEET (CSS)
Introduction
Style sheets are powerful
mechanism for adding different types of styles to any web document or web page.
It allows web designer to improve and change the appearance of the web page in
very efficient manner. It makes standard and uniformity throughout a web site.
It enables us to control rendering of styles such as fonts, color, typeface,
size, spacing, margins, and other aspects of document style. It is a style
sheet language which specifies how to incorporate style information in a style
sheet. These sheets are said to be cascade when they combine to specify the
appearance of a web page, which indicate that several style sheet can be
blended to a document. To embed style to a document <style>…. </style>
tags are used.
ADVANTAGES
·
Its
main advantage is its ability to make global change to all documents from a
single location.
·
The
primary intention of CSS is to separate document presentation from document
content written in markup language.
·
This
mechanism allows the user to give a different look to the same document,
without significant effort.
·
The
same style sheet can also be used on different documents.
·
It
reduces the development time significantly.
Content + Style =
Document
ADDING CSS
There are four different ways to
indicate style information in a document:
·
External Style Sheets- In this, style
information is written in a separate file and is referenced from an HTML
document. It is useful when same style is applied on different document.
For e.g.-
<link rel=”stylesheet”
type=”text/css” href=”mystyle.css”>
·
Embedded Style Sheets- In this, style
information is placed under the style tag in the head part of the HTML page.
For e.g.-
<style>
P {
color: green;
}
</style>
·
Imported Style Sheets-. In this, style
information is embedded using @import statement. Its working is same as
linking. It allows importing a style sheet from another style sheet.
For e.g.-
<style>
@import URL (“style.css”)
</style>
·
Inline style Sheets- In this, style
information is directly incorporated into the HTML tags. This is the least
flexible styling method.
For e.g.-
<p style=”color: red”>
Hello World </p>
CASCADING RULE
·
Specificity
rule- more specific rules get preference over less specific rules.
P b {color: blue}
b {color: black}
The formal makes text under the
tag <b>,which is descendant of tag p, blue. The latter makes text under
the <b> tag black.
·
Order
rule- For conflicting rule, latter rules get preference over the earlier
rule
The order is from
highest importance to lowest importance.
Inline Style
|
Internal style
|
External style
|
Imported style
|
Browser default
style
|
Style attributes
There are mainly 6 style
attributes.
1.
Font
attributes
·
Font
size
·
Font
style
·
Font
family
·
Font
weight
2.
Color
attributes
3.
background
attribute
·
background
color
·
background
image
·
background
repeat
4.
Text
attribute
·
text
alignment
·
text
index
·
text
transformation
·
text
decoration
5.
Border
attribute
·
border
style
·
border
width
·
Border
color
6.
Margin
attribute
·
Margin
width
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