CLIENT SIDE PROGRAMMING

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UNIT 2
CLIENT SIDE PROGRAMMING
INTRODUCTION TO STYLE SHEET
“STYLE SHEET IS A COLLECTION OF FORMATTING STYLES, WHICH CAN BE
APPLIED TO A WEB PAGE.”
2.1 Benefits of the Style Sheets
Separation of style and content has many benefits:
1 Speed. Users experience of a site utilizing style sheets will generally be
quicker than sites that don‟t use the technology. „Overall‟ as the first
page will probably load more slowly – because the style sheet AND the
content will need to be transferred. Subsequent pages will load faster
because no style information will need to be downloaded – the CSS file
will already be in the browser's cache.
2 Maintainability. Holding all the presentation styles in one file significantly
reduces maintenance time, and reduces opportunity for human errors
by reducing the maintenance tasks.
3 Accessibility. Sites that use CSS with either XHTML or HTML are easier to
draw so that they appear extremely similar in different browsers
4 Customization. If a page's layout information is all stored externally, a user
can decide to disable the layout information entirely, leaving the site's
bare content still in a readable form. Site authors may also offer
multiple stylesheets, which can be used to completely change the
appearance of the site without altering any of its content.
5 Consistency. Because the semantic file contains only the meanings an
author intends to convey, the styling of the various elements of the
document's content is very consistent. For example, headings,
emphasized text, lists and mathematical expressions all receive
consistently applied style properties from the external stylesheet.
Authors need not concern themselves with the style properties at the

time of composition. These presentational details can be deferred until
the moment of presentation.
6 Portability. The suspension of presentational details until the time of
presentation means that a document can be easily re-purposed for an
entirely different presentation medium with merely the application of a
new stylesheet already prepared for the new medium and consistent
with elemental or structural vocabulary of the semantic document.
2.2 Disadvantages of the Style Sheets
Currently specifications (for example, XHTML, XSL, CSS) and software tools
implementing these specification are only reaching the early stages of maturity. So
there are some practical issues facing authors who seek to embrace this method of
separating content and style.
1 Lack of semantic vocabulary. HTML offers a rich, but limited
vocabulary of semantic elements (for example paragraph, quote,
emphasis). The migration of HTML to the extensible XHTML may
eventually speed the proliferation of richer semantic vocabularies
to apply generalized styles to.
2 Complex Layouts. One of the practical problems is the lack of proper
support for style languages in major browsers. Typical web page layouts call for
some tabular presentation of the major parts of the page such as menu
navigation columns and header bars, navigation tabs, and so on. However,
deficient support for CSS and XSL in major browsers forces authors to code
these tables within their content rather than applying a tabular style to the
content from the accompanying stylesheet.
3 Narrow Adoption without the Parsing & Generation Tools. While the
style specifications are quite mature and still maturing, the software
tools have been slow to adapt. Most of the major web development tools
still hold a mixed presentation-content model. So authors and
designers looking for GUI based tools for their work find it difficult to
follow the semantic web method. In addition to GUI tools, shared
repositories for generalized stylesheets would probably aid adoption of
these methods.
The style sheet consists of the following components:
2.3 Style Rule

“A STYLE RULE IS A SET OF HTML TAGS SPECIFYING THE FORMATTING
ELEMENTS.”
Style rules can be applied to selected contents of a web page.
A style rule can basically be split into two parts:
(a) Selector: A selector is a string that identifies what elements the
corresponding rule applies to and is the first part of the rule.
(b) Declaration: This part of the rule is enclosed within curly brackets. A
declaration has two sections separated by a colon. The section
before the colon tells the property, and the section after the colon is
the value of that property.
The syntax of a style rule is as follows:
Selector (property : value)
Where,
Selector = Any HTML tag
Property = Attribute like font color, font size, etc.
Value = Setting for the attribute
e.g. H1 { color : blue }
H1 is the selector, color : blue is the declaration color is the property and blue is the
value.
2.4 Selectors
The selectors in the style rule basically are categorized into:
2.4.4.1 Simple Selectors
These are the easiest to use. A SIMPLE SELECTOR DESCRIBES AN
ELEMENT IRRESPECTIVE OF ITS POSITION IN THE DOCUMENT
STRUCTURE. The H1 heading identifier is a typical example of simple
selector.
H1 { Color : blue }
2.44.2 HTML Selectors

These selector use the names of HTML elements without brackets. So the
HTML <P> tag becomes P.
Example: In this example, while defining the style, the P element does not
have brackets.
<HTML>
<HEAD>
<STYLE>
P { font – style : italic ; font – weight : bold ; color : limegreen ; font –
size : 12 pt ; line – height : 16 pt }
</STYLE>
</HEAD>
<BODY>
<P> these selectors use the names of HTML elements. The only
difference is that the brackets are removed. </P>
</BODY></HTML>
2.5.4.3 Class Selectors
The class selector gives authors the ability to apply styles to specific parts
of a document and do not necessarily to the whole document
The syntax is:
<STYLE>
Class selector
. Class Name Class selector { Property : Value }
</STYLE>
<BODY>
<P Class = “Class Name”>
Class attribute
</BODY>
Class name can be any valid string of characters.
The class selector is preceded with a dot (.) called the flag character
Class selector can be applied to any of the HTML elements by using the
class attribute.
Example:

<HTML>
<HEAD>
<STYLE>
. note { color : blue }
. syntax { color : red }
P. syntax { color : red }
P { font – size : large }
</STYLE>
</HEAD>
<BODY>
<P CLASS = “syntax”> The class selector is preceded with a dot (.) called
the flag character, followed by the „Class name‟.
<P CLASS = “note”> It is better to choose class name according to their
purpose rather than a name that describes their color or style.
<H1 CLASS = “note”> The class attribute is used even to the heading tag.
</H1>
</BODY>
</HTML>
2.6.4.4 ID Selectors
Like class selection, ID selector is also used to apply style to the selected
parts of text. In this style, each ID selector has a unique identifier. An ID
selector is preceded by a hash (#) mark and to apply ID selector the ID
attribute of an HTML element is used.
The syntax is:
<STYLE>
ID Selector name
# IDSelectorName {Property : Value}
</STYLE>
<BODY>
<P ID = “IDSelectorName”>
ID Attribute

</BODY>
Example:
<HTML>
<HEAD>
<TITLE> ID SELECTOR </TITLE>
</HEAD>
<BODY>
<STYLE>
#Control { color : red }
</STYLE>
<H2 Id = “Control”> Fire is this color </H2>
<BR>
<H2> The browser controlled display of an H2 heading </H2>
<BR>
<P ID = “Control”> Applying an ID to a paragraph element. </P>
<BR>
<P> This is paragraph that has no style applied </P>
</BODY>
</HTML>
2.7.4.5 Contextual Selectors
Consider a situation where, some tags are under H1 that are italics. Now
to change any of their color to red following code could be used:
H1 { color : red }
I { color : red }
But in the above code, all type italicized tags turn to red. This is because
of the line 2 of the code.
To avoid such situation contextual selectors can be used. Contextual
selectors can be used to combine number of simple selector separated by a
space.
The above code now can be rewritten as:
H1 I { COLOR : RED }
The concept of contextual selectors support inheritance
Example:

<HTML>
<HEAD>
<TITLE> contextual selectors </TITLE>
<STYLE>
body {
Color : Magenta;
Background : white;
Font – family : Arial;
}
ul {
color : aqua
}
</STYLE>
</HEAD>
</HTML>
2.5 Ways of Incorporating Styles in HTML document
There are four ways of incorporating style sheets in HTML document, which are:
 Including style information within HTML
 Embedding a style sheet
 Linking to an external style sheet
 Importing a style sheet
2.5.1 Including Style Information Inline – Inline Styles
Inline style declaration is the most basic style rule, which can be applied to individual
elements in the web page, Inline styles are implemented by using style attributes with
the HTML tags.
The syntax is :
<HTML TAG STYLE = “PROPERTY : VALUE”>

e.g.
<P STYLE = { COLOR : OLIVE }>
Example: The style rule is applied to H1 tag by specifying it in the STYLE attribute.
<HTML>
<BODY>
<H1 STYLE = “Color : limegreen”> This is a style applied to an H1 element </H1>
<H1> This is the default display of an H1 element </H1>
</BODY>
</HTML>
The color property sets the color of the first H1 element to limegreen color and the
second one remains the default since no style attribute is applied.
2.5.2 Embedding Style Sheet
More than one style rule can be grouped by using <STYLE>……….</STYLE> tag
pair unlike of applying it individually in inline style. Each of these tags when used
in the BODY of the HTML code will apply the style rules.
The syntax is:
<HTML>
<HEAD>
<STYLE>
Style Rules

</STYLE>
</HEAD>
<BODY>
…………
…………
…………
</BODY>
</HTML>
Example,
<HTML>
<HEAD>
<STYLE>
H1 { font – family : Arial }
H1 { Color : limegreen }
</STYLE>
</HEAD>
<BODY>
<H1> This is the H1 element </H1>
<H2> This is the H2 element </H2>

………
</BODY>
</HTML>
2.5.3 Grouping Style Rules
Same style properties can be applied to more than one elements in a document by
grouping the style rules as shown below:
<HTML>
<HEAD>
<STYLE>
H1, H2 { Color : red ; font-family : Arial }
</STYLE>
</HEAD>
<BODY>
<H1>This is the H1 element </H1>
<H2>This is the H2 element </H2>
<H3>This is the H3 element with its default style as displayed in the browser </H3>
</BODY>
</HTML>
The above methods of modifying styles of elements are within the same page. To apply
similar settings for all the pages in the website, all the style rules should be put into a

style sheet File and then imported or linked with the HTML document. This method of
linking or importing is called CASCADING STYLE SHEETS (CSS).
2.5.4 Linking to an External Style Sheet
For constructing a CSS, first style rules must be written in a document and saves in a
separate file with extension of CSS. The syntax for linking to an external style sheet is:
<HTML>
<HEAD>
<LINK REL = “STYLESHEET” HREF = “Dictionary path where the style sheet is saved”>
</HEAD>
<BODY>
………
………
</BODY>
</HTML>
Where REL = STYLESHEET – Relation to the external document in a style sheet.
For example, consider a style sheet definition which specifies two styles:
 a global style applies to all <H2> element (green, arial font family, normal size)

 a generic style class named warning (red, bold, italic) which will apply to any
element which uses that class.
Style 1. CSS has the following code:
<STYLE>
H2 { COLOR : limegreen;
font – family : “Arial”;
font – size : normal
}
Warning { color : red;
font – weight : bold;
font –style : italic
}
</STYLE>
HTML file:
<HTML>
<HEAD>
<TITLE> Changing the rules </TITLE>
</HEAD>
<H2> Changing the rules is fun </H2>
<BR>

<P class = “warning”> Changing the rules may not be such fun
<H2> The H2 element again </H2>
</HTML>
TYPE = “text / css”
2.5.5 Importing a Style Sheet
Importing a style sheet, automatically pulls, the style rules into the document for
use. Once imported, changes made to the style sheet will not be reflected in the web
page into which it has been imported. This problem can be avoided by linking the
style sheet to the main document rather than importing it.
The syntax is:
<HTML>
<HEAD>
<STYLE TYPE = “TEXT / CSS”>
@ IMPORT URL (The Path) ;
</STYLE>
</HEAD>
<BODY>
………
………
</BODY></HTML>
2.5.6 Style Sheet Properties

Font Properties.
(a) font-family – Denotes font
(b) font-size – Denotes the size of the text.
(c) font-style – Denotes the style of the text for example normal, bold, italic
etc.
(d) font-weight – Denotes the weight or darkness of the font. This value
ranges from 100 to 900 increments of 100.
Text Properties.
(a) Letter-spacing – Denotes the space between letters (in inches(in),
centimeters (cm), millimeter (mm), or points (pt), etc.).
(b) Word-spacing – Denotes the space between words (in inches(in),
centimeters (cm), millimeter (mm), or points (pt), etc.).
(c) Vertical-Align – Denotes the vertical positioning of the text and images,
with respect to the baseline. The possible values include baseline, sub, top,
text-top middle percentage values, etc.
(d) Text-Align – Specifies the alignment of the text. Possible values: center,
justify, etc.
(e) Text-indent – Denotes margins. This property sets the indentation for text
in the first line of block level element.
(f) Text-decorate – Denotes the text‟s decoration. The standard values for
this property include blink, line – through over line underline etc.

Color and Background Properties.
(a) Color – Denotes the color property, used to set text color.
(b) Background-color – This property sets an element‟s background color.
(c) Background-image – Associates a background image with an element.
(d) Background-position – Specifies how a background image is positioned.
Box Properties.
Block style elements such as the <P> element can be considered as
rectangular boxes on the screen. These properties include:
(a) Margin Properties – The margin values should be in length like 15 pt. etc.
The individual margins for a block element can be set using margin-top,
margin-rigid, margin-bottom, or margin-left.
(b) Border Properties:
 Border-style – Used to set the appearance of the borders. The
values can include solid, double, groove, ridge, etc.
 Border-width – The width of the border is specified here. The
individual border width can be set using border-top-width
border-right-width, border-bottom-width, border-left-width etc.
 Border-color – Border may be assigned a color.

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