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What is CSS ?Why use CSS ?How does it work ?
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What is CSS ?
It is NOT the same as HTMLIt is a different language (code)It is more complex than HTML
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What is CSS ?
A language for specifying appearanceSeparate FORM from CONTENTHTML for the content (data)CSS for the form (presentation)
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Content
<body> … </body><p> Lots of text </p><h1> Titles </h1><img src=”picture.jpg” /><ol> … </ol><div> … </div>etc.
Data/Structurecolor:green;margin:20px;padding:5px;border:2px solid black;background:yellow;font-weight:bold;etc.
Visual Style
Form vs
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<body> … </body><p> Lots of text </p><h1> Titles </h1><img src=”picture.jpg” /><ol> … </ol><div> … </div>etc.
HTMLcolor:green;margin:20px;padding:5px;border:2px solid black;background:yellow;font-weight:bold;etc.
CSS
Content Form vs
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Why use CSS ?
More powerful for controlling visuals than HTMLMore efficient for browsers than HTMLMore flexible for complex sites
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Why use CSS ?
Separation of CONTENT and FORM is importantEasily change the look without touching the contentDifferent people do those jobs
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Why use CSS ?
http://www.csszengarden.com/
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How does CSS work ?
Define a style specificationApply it to HTML elements
<body style="background:goldenrod;">
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How does CSS work ?
Inline stylesInternal style sheetsExternal style sheets
3 Methods
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Inline styles
<body style="background:goldenrod;"><hr style="height:3px;background-color:dimgray;"><ul style="list-style-image:url('cd-bullet.png');"><div style="background:yellow; margin:20px;}">
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But ...
What if you had 100<div style=”…”>boxes</div>
that you wanted to restyle ???
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Internal style sheets<head> <title>Davidson @ RHS</title> <style> body {background:goldenrod;} hr {height:3px;background-color:dimgray;} ul {list-style-image:url('cd-bullet.png');} div {background:yellow; margin:20px;} </style></head>
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Internal style sheets <style> body {background:goldenrod;} hr {height:3px; background-color:dimgray;} ul {list-style-image:url('cd-bullet.png');} div {background:yellow; margin:20px;} </style>These apply to ALL occurrences of the HTML element on the page.
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But ...
What if you want to apply different styles to
different occurrences of an element on the page ???
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<div>!<p>Today some very misguided person set a fire in one of the bathrooms at school. This was not a good thing, by any means. But it spawned a wonderful, impromptu assembly in the gym while we waited to go back to classes.</p>
</div>
<div>!<p>I played some of one version of "Hallelujah" in my classes today and was pleasantly surprised to see that many of my students responded to it and know it from some recent popular culture appearances.</p>
</div>
For instance ...
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<style> div {background:yellow; margin:20px;} </style>
Using this style definition would make all of the <div>s have yellow backgrounds.
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There is a way...
We can give different names to different styles, and apply them to different occurrences
of an element.
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CSS Classeselement.class
<style>div.bright {background:yellow;}div.neon {background:green;}
</style>
<div class="bright"><div class="neon">
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<div class="bright">!<p>Today some very misguided person set a fire in one of the bathrooms at school. This was not a good thing, by any means. But it spawned a wonderful, impromptu assembly in the gym while we waited to go back to classes.</p>
</div>
<div class="neon">!<p>I played some of one version of "Hallelujah" in my classes today and was pleasantly surprised to see that many of my students responded to it and know it from some recent popular culture appearances.</p>
</div>
<style>div.bright {background:yellow; margin:20px;}div.neon {background:green; margin:20px;}
</style>
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Internal style sheets
Blog Page Example