CSS Overview

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					                               CSS: Cascading Style Sheets
I.    Overview: Why Use CSS?
      •   You should code your web pages structurally, logically, not visually.
          Don’t think, “I want the text big, so I’ll use <h1>.” (visual coding)
          Think instead, “This is a heading: <h1>; this is a paragraph: <p>; this is a list: <ul> or <ol>…”
          (structural or logical coding)
      •   With CSS, you can separate the content and structural html code, from the “formatting.” Formatting
          in CSS is called “style.”
II.   Three Levels of CSS:
      •   “Cascading” means there are three levels of CSS, and they have a particular order of preference.
      •   Each level has its own pros and cons (advantages and disadvantages), and its best ways to be used.

      1. External (also called “linked”):
         • A separate file that contains only CSS styles, no html.
         • File called a “style sheet.” File name: name.css (ex: style.css or stylenew.css)
         • A <link> tag in the <head> section of a web page links to the style sheet file.
         • External style sheet settings can be “overridden” by internal and inline CSS; external style sheets
             are the last in the order of preference.
         • PROS: One style sheet can define style for many web pages or an entire website. Change settings
             in the style sheet and many pages changed all at once. External style sheets are the best way to
             use CSS, even though they are the last in the order of preference.
         • CONS: Most generally applied: will apply to all elements in all pages linked to the style sheet.
             Last in order of preference means overridden by internal and inline styles.
      2. Internal (also called “embedded”):
         • A style section in the <head> section of an individual web page.
         • Code is <style> … </style> with all the CSS between open and close <style> tags.
         • Internal styles override external style sheets, but are overridden by local styles; they are second in
             the order of preference.
         • PROS: All CSS is in one place in the web page: in <style> in the <head>. Good to use when one
             page has different styles than all the other pages (which are linked to the external style sheet).
         • CONS: Internal is redundant, because you need to have it in every web page file. If you want to
             change a style throughout a website, you’ll need to change the style in every <style> section of every
             page… You should try to avoid using internal CSS as much as possible!
      3. In-line (also called “local”):
         • Inline CSS is embedded into individual html tags; they are “local” to a single tag.
         • Inline CSS is a blend of CSS and HTML: it uses html syntax to define css styles as an attribute of
              the html tag.
         • Inline CSS is first in order of preference; it overrides both internal and external styles.
         • PROS: Good for when you want to apply a certain style to just one or a few tags. Gives you the
              most specific local control.
         • CONS: Defeats the purpose of separating the content and logical code from the style, because the
              CSS is “all mixed up” with the HTML code. You should try to avoid using inline CSS as much
              as possible!
III. Syntax and How to Use CSS:
    •   General Syntax:
        selector       {property:value; property:value; property:value;}
        for example:
        h1 {text-align:center; color:red; font-size:28px;}
        Inline syntax is different (see blow)
    1. External style sheet syntax:
       • Two parts to external CSS;
           1)        The <link> tag in the <head> section of each web page file; and
           2)        The external style sheet file itself.
        •   In <head> section add:
            <link href="name.css" type="text/css" rel="stylesheet">
            where name is the name of your style sheet file.
        •   CSS syntax inside the external style sheet:
                       selector        {property:value; property:value; property:value;}
            or:
                       selector
                              {
                              property:value;
                              property:value;
                              }
            for example:
                       body
                              {
                              background:white;
                              color:#000066;
                              font-family:verdana, helvetica, arial, sans-serif;
                              font-size: 12px;
                              }

                       h1
                              {
                              font-size:28px;
                              font-weight:bold;
                              text-align:center;
                              }
    2. Internal css syntax:
        •   In the <head> section of an individual web page, include the following:
                      <style type="text/css">
                      selector      {property:value; property:value; property:value;}
            or:
                      selector
                             {
                             property:value;
                             property:value;
                             property:value;
                             }
                      </style>

    3. In-line css syntax:
        •   Inline CSS is embedded into individual html tags, like this:
                      <selector       style="property:value; property:value">
            for example:
                      <h1 style="text-align:center;color:red">
            or:
                      <p style= "font-size:x-large”>
IV. Learning CSS Property:Value Pairs:
    •   Just as there are hundreds of HTML attribute-value pairs, there are hundreds of CSS property:value
        pairs. Instead of trying to memorize them, learn to look them up:
          • In HTMLPad’s CSS Reference on the Help menu,
          • In a web design reference book, or
          • On the Internet.
    •   Best suggestion for learning and using CSS in this class: Use HTMLPad CSS Reference!
    •   A few good websites to use:
        http://www.w3.org/MarkUp/Guide/Style
        http://www.westciv.com/style_master/academy/css_tutorial
        http://developer.apple.com/internet/css/introduction.html and many more…
        See http://teacherjohn.com/resources/webdesignresources.html for more links

				
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