cs428 web engineering lecture 06 introduction (cascading style sheet) 1
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CS428 Web EngineeringLecture 06
Introduction (Cascading Style Sheet)
2
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bscsnotes4u/webeng
CASCADING STYLE SHEET• This is the language to add presentation styling to HTML documents.
• CSS is a powerful and flexible way to add format to web page for presentation.
• Through CSS it is relatively easy to take simple page of text and images, formatted to present as fully professional webpage.
• CSS has a simple syntax, consist of selectors, properties and values it together make a style rules.
• It gives developer find ways to control over how each element of page is formatted.
• CSS styles can apply on HTML documents through several different ways.– Create an external CSS file.– Embed CSS code in HTML document.
CSS Syntax• A style rule is made of three parts:
• Selector: A selector is an HTML tag at which style will be applied. This could be any tag like <h1> or <table> etc.
• Property: A property is a type of attribute of HTML tag. Put simply, all the HTML attributes are converted into CSS properties. They could be color or border etc.
• Value: Values are assigned to properties. For example color property can have value either red or #F1F1F1 etc.
• You can put CSS Style Rule Syntax as follows:
selector { property: value; }
• Example: You can define a table border as follows:
table {
border: 1px solid #C00FDF;
}
Applying CSS• There are three ways through which you
apply CSS on your HTML doc.
Inline Internal External
Inline CSS
• You can also embed your CSS code in HTML document.
• Example:
<p style=“font-family: monospace;”>
INTERNAL CSS• <style></style> always placed between <head></head> tags.
• Example:<style>
p {line-height: 120%;
}</style>
EXTERNAL CSS FILE• External CSS file will always place between
<HEAD></HEAD> tags.
• <link rel=“stylesheet” type=“text/css”
href=“main.css” />
CSS Rules Overriding• Any inline style sheet takes highest priority. So it will
override any rule defined in <style>...</style> tags or rules defined in any external style sheet file.
• Any rule defined in <style>...</style> tags will override rules defined in any external style sheet file.
• Any rule defined in external style sheet file takes lowest priority and rules defined in this file will be applied only when above two rules are not applicable.
EXAMPLE• <head>
<style>
div {
color: #9932CC;
}
</style>
</head>
<div>
<h1>Style Sheets</h1>
<p style="font-family: monospace; color: #0000FF;">
Lorem ipsum dolor sit amet, consectetur adipiscing
elit. Pellentesque sit amet lorem ligula. </p></div>
EXAMPLE• <style>
a {
font-family: sans-serif;
}
</style>
<p style="font-family: monospace;">
Lorem ipsum dolor sit amet, consectetur adipiscing
elit. <a href=“p1.html”>Pellentesque</a> sit amet
lorem ligula. Nam pulvinar nunc ac magna
aliquam quis sodales dui elementum.
<a href=“p2.html”>Fusce a lacus leo.</a>
</p>
SELECTORS• There are three types of selectors:
Tag selectors ID selectors Class selectors
Example Tag Selector
<style>p {
font-family: sans-serif;
font-size: 15pt;
line-height: 150%;
}</style>
Tag selector
Example Class Selector
<style>.foo {
font-family: sans-serif;
font-size: 15pt;
line-height: 150%;
}</style>
<p class=“foo”> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque sit amet lorem ligula. Nam pulvinar nunc ac magna aliquam quis sodales dui elementum. Fusce a lacus leo. Maecenas ut dui eu quam condimentum sagittis. </p>
class selector
Example Class Selector<style>
p.foo {
font-family: sans-serif;
font-size: 15pt;
line-height: 150%;
}</style>
<body>
<h1 class=“foo”></h1>
<p class=“foo”></p>
</body>
class selector
Example ID Selector
<style> #p1 {
font-family: sans-serif;
font-size: 15pt;
line-height: 150%;
}</style>
<p id=“p1”> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque sit amet lorem ligula. Nam pulvinar nunc ac magna aliquam quis sodales dui elementum. Fusce a lacus leo. Maecenas ut dui eu quam condimentum sagittis.
</p>
ID selector
RULE for ID selector
• There is only be one element in a
document with a particular ID selector.
• ID selector can only be used once in
one element/tag.
Descendant Selector
<style> p a {
font-family: sans-serif;
font-size: 15pt;
line-height: 150%;
}</style>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit.. Nam pulvinar nunc ac magna aliquam quis sodales dui nunc sit elementum. <a href=“page1.html”>Donec eu nisi turpis,</a> sit amet rutrum leo.
</p>
Click <a href=“page2.html”>here</a>
Grouping Selector
• you can apply style to many selectors.• <style>
h1, p, section {
color: #35c;
font-weight: bold;
letter-spacing: .4em;
} </style>
Grouping Class & ID Selectors
• you can apply style to many selectors.
<style> #content, #footer, .supplement {
position: absolute;
left: 510px;
width: 200px;
} </style>
PSEUDO SELECTOR
<style>
a:link {
color: #008080;
} a:hover {
color: #FF0000;
}</style>
COMMENTS IN CSS
<style>
/*
p {
font-family: sans-serif;
font-size: 15pt;
}
*/
</style>
CSS – Measurement Units
• CSS supports a number of measurements
including absolute units such as inches,
centimeters, points, and so on, as well as
relative measures such as percentages and
em units. You need these values while
specifying various measurements in your
Style rules.
• Example: border: 1px solid red;
CSS UNITS of MEASURE (1/3)• # column1 {
width: 100%;
}
• p {
font-size: 12pt;
}
• p {
font-size: 1pc;
}
CSS UNITS of MEASURE (2/3)• p {
margin-left: 2ex;
}
• p {
padding-right: .25in;
}
• p {
padding-right: 10mm;
}
CSS UNITS of MEASURE (3/3)• p {
margin-left: 2em;
}
• div#main {
width: 600px;
}
CSS UNITS - Sizes• Relative length measurements:
– px (pixels – size varies depending on screen resolution)– em (usually the height of a font’s uppercase M) – ex (usually the height of a font’s lowercase x)– Percentages (of the font’s default size)
• Absolute-length measurements (units that do not vary in size):– in (inches)– cm (centimeters)– mm (millimeters)– pt (points; 1 pt = 1/72 in)– pc (picas; 1 pc = 12 pt)
• Generally 1em = 12pt = 16px = 100%
29
Unit Description Example
%
Defines a measurement as a percentage relative to another value, typically an enclosing element.
p { font-size: 16pt; line-height: 125%; }
cm Defines a measurement in centimeters. div {margin-bottom: 2cm;}
em
A relative measurement for height of a font in em spaces. Because an em unit is equivalent to the size of a given font, if you assign a font to 12pt, each “em” unit would be 12pt; thus 2em = 24pt.
p { letter spacing: 7em; }
ex
This value defines a measurement relative to a font’s x-height. The x-height is determined by the height of the font’s lowercase letter x.
p { font-size: 24pt; line-height: 3ex; }
in Defines a measurement in inches. p { word-spacing: .15in;}
mm Defines a measure in millimeters. p { word-spacing: 15mm;}
pcDefines a measurement in picas. A pica is equivalent to 12 points. Thus, there are 6 picas per inch.
p { font-size: 20pc;}
Unit Description Example
ptDefines a measurement in points. A point is defined as 1/72nd of an inch.
body {font-size: 18pt;}
px Defines a measurement in screen pixels. p {padding: 25px;}
CSS – Colors
• You can specify your color values in various
formats.
Format Syntax Example
Hex Code #RRGGBB p {color: #FF0000; }
Short Hex Code #RGB p {color: #6A7;}
RGB % rgb(rrr%, ggg%, bbb%)p { color: rgb(50%, 50%, 50%); }
RGB Absolute rgb(rrr, ggg, bbb)p { color: rgb(0, 0, 255); }
keyword aqua, black etc. p { color: teal;}
CSS Box Model • A set of rules collectively known as CSS Box Model
describes the rectangular region occupied with
HTML elements.
• The main idea is that every element’s layout is
composed of: the actual element’s content area. a border around the element. a padding between the content and the border (inside the border) a margin between the border and other content (outside the border)
Document Flow - Block Elements
Document Flow – Inline Elements
Document Flow – Larger Example