| CSS Id and Class Selector
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The class Selector
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The class selector is used to specify a style for a group of elements. Unlike the id selector,
the class
selector is most often used on several elements.
» This allows you to set a particular style for any HTML elements with the same class.
» The class selector uses the HTML class attribute, and is defined with a "."
» In the example below, all HTML elements with class="center" will be center-aligned:
Example
<html>
<head>
<style type="text/css">
.center
{
text-align:center;
}
</style>
</head>
<body>
<p class="center">Hello World!</p>
<p class="center">This is chennaisunday.</p>
</body>
</html>
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The Output is Shown Here:
Hello Friends
This is chennaisunday.
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Three Ways to Insert CSS
There are three ways of inserting a style sheet:
» External style sheet
» Internal style sheet
» Inline style
External Style Sheet
An external style sheet is ideal when the style is applied to many pages. With an external style sheet, you can change the
look of an entire Web site by changing one file. Each page must link to the style sheet using the <link> tag.
The <link> tag goes inside the head section:
<head>
<link rel="stylesheet" type="text/css" href="style.css" />
</head>
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An external style sheet can be written in any text editor. The file should not contain any html tags.
Your style sheet should be saved with a .css extension. An example of a style sheet file is shown below:
hr {color:pink;}
p {margin-left:20px;}
body {background-image:url("images/bggreen.gif");}
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 Do not leave spaces between the property value and the units! "margin-left:20 px"
(instead of "margin-left:20px") will work in IE, but not in Firefox or Opera.
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Internal Style Sheet
An internal style sheet should be used when a single document has a unique style. You define internal
styles in the head section of an HTML page, by using the <style> tag, like this:
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<head>
<style type="text/css">
hr {color:Green;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
</style>
</head>
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Inline Styles
An inline style loses many of the advantages of style sheets by mixing content with presentation. Use this method sparingly!
To use inline styles you use the style attribute in the relevant tag. The style attribute can contain any CSS property.
The example shows how to change the color and the left margin of a paragraph:
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<p style="color:green;margin-left:20px">This is a paragraph.</p>
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Multiple Styles Will Cascade into One
Styles can be specified:
» inside an HTML element
» inside the head section of an HTML page
» in an external CSS file
Tip: Even multiple external style sheets can be referenced inside a single HTML document.
Cascading order
What style will be used when there is more than one style specified for an HTML element?
Generally speaking we can say that all the styles will "cascade" into a new "virtual" style
sheet by the following rules, where number four has the highest priority:
1.Browser default
2.External style sheet
3.Internal style sheet (in the head section)
4.Inline style (inside an HTML element)
So, an inline style (inside an HTML element) has the highest priority, which means that it will
override a style defined inside the <head> tag, or in an external style sheet, or in a browser (a default value).
If the link to the external style sheet is placed after the internal style sheet in HTML <head>,
the external style sheet will override the internal style sheet!
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