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Web Development

Web Development. Cascading style sheets separating content & presentation inline vs. document vs.external sub-classes of elements pseudo-elements on to programming…. Introduction to Styles and Properties.

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Web Development

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  1. Web Development • Cascading style sheets • separating content & presentation • inline vs. document vs.external • sub-classes of elements • pseudo-elements on to programming…

  2. Introduction to Styles and Properties • To ensure that future Web page authoring separates the definition of the elements in a document from how they appear, many of the display and formatting extensions that were added to the HTML language, such as the <font> element, were deprecated in HTML 4.0 and in XHTML 1.0 in favor of CSS

  3. Introduction to Styles and Properties • Cascading Style Sheets (CSS) are a standard set by the World Wide Web Consortium (W3C) for managing the design and formatting of Web pages in a Web browser

  4. Introduction to Styles and Properties • A single piece of CSS formatting information, such as text alignment or font size, is referred to as a style • Some of the style capabilities of CSS include the ability to change fonts, backgrounds, and colors, and to modify the layout of elements as they appear in a Web browser

  5. Introduction to Styles and Properties • CSS information can be added directly to documents or stored in separate documents and shared among multiple Web pages • The term “cascading” refers to the Web pages’ ability to use CSS information from more than one source

  6. CSS Properties • CSS styles are created with two parts separated by a colon: the property, which refers to a specific CSS style, and the value assigned to it, which determines the style’s visual characteristics • Together, a CSS property and the value assigned to it are referred to as a declaration or style declaration

  7. CSS Properties

  8. Common CSS Properties

  9. CSS Properties • The properties available in CSS1 are grouped into the following categories: • Color and background properties • Font properties • Text properties • Box properties • Classification properties

  10. Inline Styles • The most basic method of applying styles is to use inline styles, which allow you to add style information to a single element in a document

  11. Inline Styles • You use the style attribute to assign inline style information to an element • You assign to the style attribute a property declaration enclosed in quotation marks

  12. CSS Values • The values you can assign to a CSS property depend on what type of property it is • Some properties can be assigned a range of values

  13. CSS Values • For instance, you can assign any font name that is available on a user’s system to the font-family property • For other properties, you must assign a value from a specific set of values

  14. Length Units • Length units refer to the units of measure that you can use in a style declaration to determine the size or positioning of an element • Whether a length unit is used for sizing or positioning depends on the property and the element to which it is assigned

  15. Length Units • You assign a measurement value to a property by assigning the number that represents the measurement, immediately followed by the unit of measure

  16. Color Units • A color unit represents a color value that you can assign to a property • You can assign a color unit to a property using any one of 16 color names defined in the CSS1 specification

  17. Color Units

  18. Color Units • Most graphical computer systems use the RGB color system for specifying colors • You can also assign a color using the RGB color system

  19. Content vs. presentation • most HTML tags define content type, independent of presentation • style sheets associate presentation formats with HTML elements • Remember, HTML style sheets are known as Cascading Style Sheets, since can be defined at three different levels • inline style sheets apply to the content of a single HTML element • document style sheets apply to the whole BODY of a document • external style sheets can be linked and applied to numerous documents lower-level style sheets can override higher-level style sheets

  20. Inline style sheets • Using the style attribute, can specify presentation style for a single HTML element • within tag, list sequence of property:value pairs font-family:Courier,monospace font-style:italic font-weight:bold font-size:12pt font-size:large font-size:larger color:red color:#000080 background-color:white text-decoration:underline text-decoration:none text-align:left text-align:center text-align:right text-align:justify vertical-align:top vertical-align:middle vertical-align:bottom text-indent:5em text-indent:0.2in • <html> • <!-- style01.html --> • <head> • <title>Inline Style Sheets</title> • </head> • <body> • <p style="font-family:Arial,sans-serif; • text-align:right">This is a • right-justified paragraph in a sans serif • font (preferably Arial), with some • <span style="color:green">green text</span>. • </p> • <p>And <a style="color:red; • text-decoration:none; • font-size:larger;" • href="page01.html">here</a> • is a formatted link. • </p> • </body> • </html> • view page in browser

  21. Inline style sheets (cont.) • <html><!-- style02.html --><head> <title>Inline Style Sheets</title></head><body> <p>Here is an image <img src=“heckerb.gif" alt=“Barbara Hecker”style="margin-left:0.3in; • margin-right:0.3in; vertical-align:middle; border-style:double; border-color:yellow"> embedded in text. </p> • <ol style="list-style-type:upper-alpha"> <li> one thing <li> or another <ul style="list-style-type:square; • whitespace:pre"> <li> with this <li> or that </ul> </ol></body></html> • more style properties & values margin-left:0.1in margin-right:5% margin:3em padding-top:0.1in padding-bottom:5% padding:3em border-width:thin border-width:thick border-width:5 border-color:red border-style:dashed border-style:dotted border-style:double border-style:none whitespace:pre list-style-type:square list-style-type:decimal list-style-type:lower-alpha list-style-type:upper-roman • view page in browser

  22. Inline style sheets (cont.) • <html> • <!-- style03.html --> • <head> • <title> Inline Style Sheets </title> • </head> • <body> • <table style="font-family:Arial,sans-serif"> • <caption style="color:red; • font-style:italic; • text-decoration:underline"> • Student data. </caption> • <tr style="background-color:red"> • <th> name </th> <th> age </th> • </tr> • <tr> • <td> Chris Smith </td> <td> 19 </td> • </tr> • <tr> • <td> Pat Jones </td> <td> 20 </td> • </tr> • <tr> <td> Doogie Howser </td> <td> 9 </td> </tr> • </table> • </body> • </html> • style sheets can be applied to tables for interesting effects • view page in browser

  23. Document style sheets • inline style sheets apply to individual elements in the page • can lead to inconsistencies as similar elements are formatted differently • e.g., might like for all H1 elements to be centered • inline definitions mix content & presentation •  violates the general philosophy of HTML • alternatively, document style sheets allow for a clean separation of content and presentation • style definitions are placed in the HEAD of the page (within STYLE tags) • can apply to all elements, or a subclass of elements, throughout the page

  24. Document style sheets • document style sheets ensure that similar elements are formatted similarly • can even define subclasses of elements and specify formatting p.indented defines subclass of paragraphs • inherits all defaults of <p> • adds new features to specify this newly defined class, place class="ID" attribute in tag • note how "clean" the BODY is • <html> • <!-- style04.html --> • <head> • <title>Document Style Sheets</title> • <style type="text/css"> • h1 {color:blue; • text-align:center} • p.indented {text-indent:0.2in} • </style> • </head> • <body> • <h1>Centered Title</h1> • <p class="indented">This paragraph will have the first line indented, but subsequent lines will be flush.</p> • <p>This paragraph will not be indented. • </p> • <h1>The End</h1> • </body> • </html> • view page in browser

  25. Document style sheets (cont.) • document style sheets are especially useful in formatting tables • effectively separates content from presentation • <html> • <!-- style05.html --> • <head> • <title> Inline Style Sheets </title> • <style type="text/css"> • table {font-family:Arial,sans-serif} • caption {color:red; • font-style:italic; • text-decoration:underline} • th {background-color:red} • </style> • </head> • <body> • <table> • <caption> Student data. </caption> • <tr><th> name </th> <th> age</th></tr> • <tr><td> Chris Smith </td> <td> 19 </td></tr> • <tr><td> Pat Jones </td> <td> 20 </td></tr> • <tr><td> Doogie Howser </td> <td> 9 </td></tr> • </table> • </body> • </html> • what if you wanted to right-justify the column of numbers? • what if you changed your mind? • view page in browser

  26. Pseudo-elements • <html> • <!-- style06.html --> • <head> • <title>Title for Page</title> • <style type="text/css"> • a {color : red; • text-decoration : none; • font-size : larger} • a:visited {color : black} • a:active {color : orange} • a:hover {color : blue} • p:first-letter {font-size : large; color : white; background-color : darkblue} • </style> • </head> • <body> • <p>Welcome to my Web page. I am so • happy you are here. • </p> • <p>Be sure to visit • <a href="http://www.cnn.com">CNN</a> • for late-breaking news. • </p> • </body> • </html> • pseudo-elements are used to address sub-parts of elements • can specify appearance of link in various states • :visited :active :hover • can specify format of first line in page or paragraph • :first-line • can specify format of first letter in page or paragraph • :first-letter • Danger: changing the look of familiar elements is confusing • Careful : current browsers do not support all CSS2 features • view page in browser

  27. External style sheets • modularity is key to the development and reuse of software • design/implement/test useful routines and classes • package and make available for reuse • saves in development cost & time • central libraries make it possible to make a single change and propogate • external style sheets place the style definitions in separate files • multiple pages can link to the same style sheet, consistent look across a site • possible to make a single change and propagate automatically • represents the ultimate in content/representation separation

  28. Modularity & style sheets • ideally, the developer(s) of a Web site would place all formatting options in an external style sheet • all Web pages link to that same style sheet for a uniform look • simplifies Web pages since only need to specify structure/content tags • <html> • <!-- style07.html --> • <head> • <title>Title for Page</title> • <link rel="stylesheet" • type="text/css" • href="myStyle.css" • title="myStyle"> • </head> • <body> • <h1>Centered Title</h1> • <p class="indented">This paragraph will have the first line indented, but subsequent lines will be flush.</p> • <p>This paragraph will not be indented. • </p> • <h1>The End</h1> • </body> • </html> • <!-- myStyle.css --> • h1 {color : blue; text-align : center} • p.indented {text-indent:0.2in} • view page in browser

  29. How to show the creation date and URL information • <html><!-- style08.html --><head> <title>JavaScript preview</title></head><body> • <TABLE width="100%" border=0> • <TBODY> • <TR> • <TD align=left> • <SCRIPT language=JavaScript> • document.write("<font size=-1><i>"+document.location+"</i></font>"); • </SCRIPT> • <TD align=right> • <SCRIPT language=JavaScript> • document.write("<font size=-1><i>"+document.lastModified+"</i></font>"); • </SCRIPT> • </TR></TBODY> • </TABLE> • </body></html> • For your assignment, you need to show the date and URL of the website The page's location and last modification date should be automatically displayed at the bottom. View the source for this Web page and cut-and-paste the appropriate text into your page in order to accomplish this. • view page in browser

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