1 cascading style sheet (css). 2 cascading style sheets (css) a style defines the appearance of a...
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Cascading Style Sheet (CSS)
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Cascading Style Sheets (CSS)
a style defines the appearance of a document element.o E.g., font size, font color etc…
a style sheet: collection of styles for a Web page or Website
style sheets use common language and syntax
main style sheet standard: Cascading Style Sheets (CSS)
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CSS history
developed by WWW Consortium (www.w3c.org), the same organization that develops standards for HTML
designed to augment HTML, not replace it a whole new way of formatting Web pages provides several tools not available with standard
HTML different versions
o CSS1 released in 1996 (fonts, text, color, background)o CSS2 released in 1998 (positioning, visual formatting)o CSS3, latest standard being developed
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Benefits of style sheets
a design tool makes website design more flexible easier to maintain and modify more aesthetically interesting consistent look
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Applying a Style Sheet
Three ways to apply a style to an HTML document:
1.Inline Styles
2.Embedded Style Sheet
3.External Style Sheet
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Style types
o Inline styles styles are added to each tag within the HTML file style only affects that particular tag
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Using inline styles
format a single section, better use inline style syntax
<tag style=“style declarations”>o tag is the name of an HTML element (h1, h2, p, etc)o style declarations
the styles defined for the particular tag must be enclosed within double quotation marks use semi-colon separate multiple attributes <tag style=“attribute1:value1; attribute:value2”>
o e.g.<h1 style="text-align: center; color: red">
But what if there are same tags appearing multiple times in the webpage and you want to format all of them uniformly
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Style types (contd.)
o Inline styles styles are added to each tag within the HTML file style only affects that particular tag
o Embedded or global styles applied to an entire HTML file allowing the Web designer to modify the
appearance of any tag in the document
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Creating an embedded style
embedded style, a style applied to various sections within a Web page
use <style> tag within the <head> … </head> section
within <style> tag, enclose style declarations
syntax <head>
<style type=“text/css”>
style declarations
</style>
</head>
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Embedded Style syntax for style declaration:selector{attribute1:value1; attribute2:value2; ...}
o collection of attributes and values
selector o identifies an element in your document, e.g., a heading o identifies attributes and values within the braces for that
element
example<style type="text/css"> h1 {text-align: center; color: red}
</style>
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Embedded Style (contd.) Simple Practice exercise:
Using Embedded styles, convert “course description” and “reference texts” in main.html to blue
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Grouping selectors What if there are many tags or blocks which follows
the same style throughout the page?
apply the same declaration to a group of selectors by including all of the selector names separated by commas
<style type=“text/css”>
h1, h2, h3, h4, h5, h6 {text-align: center; color: red}
</style>
Now the next level!
Just the way we changed the styles uniformly in a single webpage, how about applying that across multiple webpages, i.e., your website
We now need an external style sheet
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Style types (contd.)
o Inline styles styles are added to each tag within the HTML file style only affects that particular tag
o Embedded or global styles applied to an entire HTML file allowing the Web designer to modify the
appearance of any tag in the document
o Linked or external style sheets placed in an external file, linked with Web pages allowing Web designer to modify the appearance of
tags in several documents across the website
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Creating an external style sheet
1. Crate a new text file
2. Save it using the extension “.css”,
3. Place your styles here
Within a style sheet, <style> tag is NOT needed, only need style declarations
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Creating an external style sheet
Create a text file containing style declarations/* Author: author name */
h1, h2, h3, h4, h5, h6 {text-align: center; color: red}
Name the file: mystylesheet.css
Remember: o Only external stylesheet creation not sufficiento Need to link the stylesheet and the html pages where you
need the styles
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Linking to style sheets with <link>
Example: link to a style sheet named “mystylesheet.css,”
<link rel="stylesheet" href="mystylesheet.css" type="text/css" />
Placement within <head> … </head> of the webpage where you need the styles
Style Conflict
Apply external, embedded and inline all three types of styling with h1 tag
o External: Text-align: center and color: red
o Embedded: Text-align: center and color: blue
o Inline: Text-align: center and color: green
What is the result?
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Style precedence
in case of styles conflict, precedence is determined in the following order:
1.an inline style overrides any embedded style or external style sheet
2.an embedded style overrides an external style sheet
3.an external style sheet overrides the internal style rules set by the Web browser
Understanding Cascading Order
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Style Inheritance If a style is not specified for an element, it
inherits the style of its parent element. This is called style inheritance
body {color: green}
p {color: red}
In the above example, the body element is the parent element
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Practice exercise All the elements in my unordered
(bulleted) list must be red throughout the website
All the elements in my ordered (numbered) list must be blue throughout the website
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CSS Part 2
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What we will cover today…
1. Managing Font-size2. Letter and word spacing3. Text appearance and attributes4. Hyperlinks appearance and attributes
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Managing font size in CSS, use font-size attribute to manage font sizes
o body {font-size: some value}
font sizes can be expressed in 4 ways1. as a unit of length
1. Absolute unit2. Relative unit
2. as a descriptive keywords3. with a keyword expressing the size relative to the font
size of parent element4. as a percentage of the parent element
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1. Unit of length: Absolute units
use unit of length, absolute units or relative units
o absolute units define the font size based on one of the following standard units of measurement:
mm (millimeter), cm (centimeter), in (inch), pt (point; 1pt=1/72in) pc (pica; 1pc=12pt)
relative unit expresses the font size relative to a size of a standard charactero em unit is equal to the width of capital letter “M” in
browser’s default font sizeo ex unit is equal to the height of a small “x” in default font
size
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1. Unit of length: Relative units
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1. Unit of length: Pixels
a pixel is the smallest element recognized by the monitor
text that is 10 pixels high may be perfectly readable at a low-resolution (e.g., 640 x 480) monitor, but it can become unreadable at high-resolution (e.g., 1024 x 768) monitor
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2. Descriptive keywords
seven descriptive keywords for font sizeo xx-smallo x-smallo smallo mediumo largeo x-largeo xx-large
Examplebody {font-size: medium}
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3. Keywords: smaller, larger
Size relative to parent element
using keywords “larger” and “smaller,” o makes the font one size larger or smaller than
the size of parent element
o example: to make <p> paragraph text one size larger than the body text:
body {font-size: medium}
p {font-size: larger}
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4. Font size as percentage of parent tag
The font size of bold content (defined by <b> tag) is 150% of the size of surronding text (where the font size is defined by <body> tag)
Text Appearance and Styling
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Specifying letter, word spacing set the space between individual letters
i n d i v i d u a l l e t t e r s letter-spacing attribute
letter-spacing: size change the spacing between individual words
individual words word-spacing attribute word-spacing: size
size can beo any number expressed in the same measuring units used to describe
font size (inches, millimeters, centimeters, em units, etc.)
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Special text attributes
CSS provides three attributes for special text effects:
1.text-decoration2.text-transform3.font-variant
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text-decoration attribute
attribute name: text-decoration values
o none (basically default; no change)o underlineo overlineo line-through
examples
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text-transform attribute
attribute name: text-transform attribute value:
o capitalize capitalize the first letter of each word in a paragraph
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text-transform attribute
attribute name: text-transform attribute value:
o uppercase display the text in all capital letters
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text-transform attribute
attribute name: text-transform attribute value:
o lowercase display the text in all lowercase letters
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text-transform attribute, example
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font-variant attribute
font-variant attribute create small caps
small caps are capital letters that are the same size as lowercase letters
syntaxfont-variant: small-caps
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font-variant attribute, example
Contextual Selector
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Working with style inheritance Web pages invariably have elements (e.g.,
tags) placed within other elements sample tree structure of Web elements
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Parent and descendant elements
an element that lies within another element is called a descendant or descendant element o e.g., in previous slide, <b> tag is a descendant of <p>
tag an element that contains another element is
called the parent or parent element.o e.g., <body> tag is the parent of all other tags used to
format the Web contents using the principle of inheritance, styles defined
for a parent tag are transferred to its descendants tags
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Contextual selectors
use tree structure to better control styles o apply a style only to direct descendant of a
parent element, use syntax: e1 e2o e1 and e2 are the names of HTML elements (i.e.
tags) and e2 is directly below e1 in the tree structure of elements
o example: li b {color:blue}only changes the color of the boldface text
residing within a <li> tag to blue
not all browsers support contextual selectors
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Hyperlink appearance and attributes Hyperlink styling
What is the tag for hyperlinks?
Introduce the tag for hyperlink as a selector in CSS
All the attributes discussed so far would work when applied in CSS
Hyperlink appearance change
By default, hyperlinks are blue and have underline
1. Change them to red hyperlinks and no underline (default for my website)
2. Change them to red hyperlinks, small caps with lines both above and below the links
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Hyperlink Special Selector
a is the general selector
Link: used for un-visited linko a:link
Visited: used for visited link.o a:visited
Active: used for the link when it is clicked. o a:active
Hover: used for the link when the mouse hovers over ito a:hover
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Practice exercise
Write a CSS file with all the Styles as defined below for the hyperlinks:
The hyperlinks must be color green with underline text-decoration.
While hovering over the hyperlink with mouse, the hyperlinks must turn UPPERCASE TEXT, color blue and without any underline.
The visited hyperlinks must turn into strike through line.
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