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Cascaded Style Sheets (CSS)

Learn about cascading style sheets (CSS) and how to apply styles, save time, maintain consistency, and control layout. Explore advantages, types of styles, and strategies for creating and linking external style sheets.

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Cascaded Style Sheets (CSS)

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  1. Cascaded Style Sheets (CSS) Ahmad Al Kawam

  2. The Breakdown • All web pages can be broken down into bucketized content areas • These areas can updated by changing the code on every page, - or - • By using cascading style sheets!

  3. Advantages of Style Sheets • Saves time • Easy to change • Keep consistency • Give you more control over layout • Use styles with JavaScript => DHTML • Make it easy to create a common format for all the Web pages

  4. Applying a single style sheet to multiple documents

  5. Basic Structure of a Style • Each definition contains: • A property • A colon • A value • A semicolon to separate two or more values • Can include one or more values • h1 {font-size:12pt;color:red}

  6. Style Precedence • External style sheet • Embedded styles • Inline styles

  7. Three Style Types • Inline styles • Add styles to each tag within the HTML file • Use it when you need to format just a single section in a web page • Example • <h1 style=“color:red; font-family: sans-sarif”>IU</h1>

  8. Three Style Types • Embedded or internal styles • A style is applied to the entire HTML file • Use it when you need to modify all instances of particular element (e.g., h1) in a web page • Example • <style> • h1 {color:red; font-family:sans-serif} • </style>

  9. Creating an Embedded Style <head> <title>Embedded Example</title> <style> (default is “text/css”) Style declarations </style> </head> • A style declaration: • Selector {attribute1:value1; attribute2:value2; …} • Selector = an element in a document (e.g., a header or paragraph)

  10. An Example of an embedded style <head> <title>Getting Started</title> <style type=“text/css”> h1 {font-family: sans-serif; color: orange} </style> </head>

  11. Three Style Types • External style sheets • An external style sheet is a text file containing the style definition (declaration) • Use it when you need to control the style for an entire web site • Example • h1, h2, h3, h4, h5, h6 {color:red; font-family:sans-serif} • Save this in a new document using a .css extension

  12. Creating an External Style Sheet • Open a new blank document in Notepad • Type style declarations • h1 {color:red; font-family:sans-serif;} • Do not include <style> tags • Save the document as filename.css

  13. Linking to Style Sheets 1 • Open an HTML file • Between <head> and </head> add • <link href=URL rel=“relation_type” type=“link_type”> • URL is the file.css • Relation_type=“stylesheet” • Link_type=“text/css” • Save this file and the .css file in the same web server directory

  14. An example of an external style sheet with an original html file <head> <title>Getting Started</title> <link href=“scraps.css” rel=“stylesheet” type=“text/css” /> </head> h1 {font-family: sans-serif; color: orange} b {color: blue} Text file of css named “stylesheet” html file

  15. Style Sheet Strategies • Wherever possible, place your styles in external style sheets • Take advantage of the power of CSS to have control over an entire Web site

  16. Style Sheet Strategies • At the top level of your web site: define a default global.css style sheet • Refine styles at sublevels with a section.css style sheet • Try to avoid using styles in tags

  17. Attribute Selectors • Create an attribute selector to select an element based on the element’s attributes.

  18. Using IDs and Classes • Use an id to distinguish something, like a paragraph, from the others in a document. • For example, to identify a paragraph as “head”, use the code: <p id=“head”>… </p>

  19. Working With Ids • To create an ID for a specific tag, use the property: • <tag ID=id_name> • To apply a style to a specific ID, use: • #id_name {style attributes and values}

  20. Classes • HTML and XHTML require each id be unique– therefore an id value can only be used once in a document. • You can mark a group of elements with a common identifier using the class attribute. <element class=“class”> … </element>

  21. Applying a style to a class

  22. Working With Classes • To create a class, enter the following in the HTML tag: • <tag CLASS=class_name> • <h1 CLASS=FirstHeader>IU</h1> • class_name is a name to identify this class of tags • To apply a style to a class of tags, use: • tag.class_name {style attributes} or • .class_name {style attributes}

  23. Working With Classes and Ids • The difference between the Class property and the ID property is that the value of the ID property must be unique: • you can’t have more than one tag with the same ID value • You can apply the same Class value to multiple document tags

  24. Working With DIV • <DIV> tag is used for blocks of text, e.g., paragraphs, block quotes, headers, or lists • To create a container for block-level elements, use: • <DIV CLASS=class_name> • Block-level elements • </DIV> • Class_name is the name of the class • You can substitute the ID proper for the Class property (with ID, the syntax for CSS style, #id_name {style attributes and values}

  25. Working With <DIV> DIV.Slogan {font-weigh:bold} style Maxwell…: “We teach… Resulting text <DIV CLASS=Slogan>Maxwell Scientific’s new Slogan is:<BR>”We teach science”</DIV> HTML code

  26. CSS for Page Layout • CSS manipulates the size and location of block-level elements • Block-level elements in HTML: • Heading tags, e.g., <H1>, <H2> • <p> • <blockquote> and <address> tags • List tags, e.g., <ul>, <ol>, <dl> • <div> • <body> • <hr> • <img>

  27. CSS for Page Layout • Parts of the block-level elements: • Margin • Border • Padding

  28. padding border margin CSS for Page Layout I appreciate the prompt delivery of the pack of star disks.

  29. Controlling the Margins • To define the margins of an element, use: • margin:value • where value = a length value (“em” is often used), a percentage (a margin proportional to the element’s width, or auto

  30. Controlling the Margins • To set margins on a side, use: • margin-top • margin-right • margin-bottom • margin-left • E.g., LI {margin-left:2em; margin-right:2em; margin-top:1em; margin-bottom:1em}

  31. Setting the Padding Size • To define padding, use: • padding: value • where value = a length value or a percentage (a padding proportional to the element’s width)

  32. Setting the Padding Size • To set margins on a side, use: • padding-top • padding-right • padding-bottom • padding-left

  33. Formatting the Border • Border can be set in three ways: • border-width • border-style • border-color

  34. Formatting the Border • To set the border, use: • border:width_value style color • To set borders on a side, use: • border-top • border-bottom • border-left • border-right

  35. Formatting Width & Height of Block-Level Boxes • To set the width of a block-level element, use: • width:value • height:value • where value can be a length value, a percentage, or auto • E.g., textarea {width:225px; height:100px}

  36. Using the Float Attribute • To float (wrap) a block-level element, use: • float:margin • Where margin = right, left, none • To prevent an element from wrapping, use: • Clear:margin • Where margin=right, left, both, none

  37. Using the Float Attribute float:right width:50px clear:right float:right width:50px

  38. Formatting Hypertext Links • To remove the style of underlining hypertext, use: • A {text-decoration:none} • 4 types of hyperlinks can be modified: • A:visited {styles for previously visited links} • A:link {styles for links that have never visited} • A:active {styles for links that are currently being clicked} • A:hover {styles when the mouse cursor is hovering over the link}

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