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  1. CSS Cascading Style Sheets

  2. Objectives • Using Inline Styles • Working with Selectors • Using Embedded Styles • Using an External Style Sheet • Applying a Style to a Web Site • Understanding Cascading Order

  3. http://www.w3schools.com/css/ Great tutorial – Go look

  4. Style Sheets • In HTML, want the content of the documents clearly separated from the document's presentation layout. • Styles sheets define how HTML elements are to be displayed

  5. Cascading Style Sheets (CSS) • Like HTML, style sheets must use a common language and follow common rules. This language is known as Cascading Style Sheets, CSS. • CSS has been developed by the WWW Consortium (www.w3c.org organization that develops standards for HTML). • CSS is designed to augment (not replace) HTML.

  6. Styles • Styles can be specified • inside a single HTML element (Inline) • inside the <head> element of an HTML page (Internal) • or in an external CSS file. (External)

  7. Inline Style (in body) • An inline style loses many of the advantages of style sheets by mixing content with presentation. Use this method sparingly. Inline styles are easy to use and interpret because they are applied directly to the elements they affect.

  8. Inline Style • To use an inline style you use the style attribute in the relevant tag. The style attribute can contain any CSS property. <element style=“property1: value1; property2:value2; …>

  9. Inline Style • Enclose the properties and values in quotes. • Separate properties with a semicolon. <p style="color: red; margin-left: 20px "> paragraph </p>

  10. Inline Style <body><h3 style=“font-family:Arial, font-style:italic; color:green”> This is H3, Arial, italic and green </h3> <h3>This is simply H3</h3> </body> This is H3, Arial, italic and green This is simply H3

  11. Syntax • The CSS syntax for internal and external styles is made up of three parts: selector {property: value} • The selector is normally the HTML element/tag you wish to define, the property is the attribute you wish to change, and each property takes a value.

  12. Syntax • The property and value are separated by a colon and surrounded by curly braces: body {color: black} • If  the value is multiple words, put quotes around the value. • Separate properties with a semi-colon. p {font-family: “sans serif”;color: red}

  13. Background • Background colors can be applied to almost any element in a Web page not just the page itself. H1 {background-color: rgb(204,102,255)} This is an H1 header with a purple background

  14. Background • background-image : url(file.jpg) • examples\css\style-background.html • http://www.w3schools.com/css/css_background.asp

  15. Comment • /* This is a CSS comment. */ • Same as JavaScript multi-line comment.

  16. Grouping • Separate selectors with a comma: • h1,h2,h3,h4,h5,h6 { color: green } • All header elements will be green.

  17. TopStyle • Software that generates correct syntax. • It’s on the machines in the lab. • It can be downloaded for free. • Go see it.

  18. Internal (Embedded) Style Sheet • Applies to a single document (HTML file) • Internal styles are embedded in the head section : <head> <style type="text/css"> hr {color: sienna} p {margin-left: 20px} </style> </head>

  19. Internal (Embedded, Global) Style Sheet <head><style> h3 {font-family:Arial; font-style:italic; color:green}</style> </head> <body> <h3>This is H3, Arial, italic and green</h3> <h3>And so is this H3</h3> </body> This is H3, Arial, italic and green And so is this

  20. External Style Sheet • An external style sheet is a text file that contains style declarations • It can be linked to any page in the site, allowing the same style declaration to be applied to the entire site • An external style sheet can be written in any text editor. The file should not contain any html tags. It should be saved with a .css extension.

  21. External Style Sheet • Example: hr {color: sienna} p {margin-left: 20px} • Notes: • No spaces between the property value and the units: 20px • This is the entire file. Within a style sheet, you don’t need <style> tags, just the style declarations.

  22. External Style Sheet • An external style sheet can control the appearance of many web pages. • Each page must link to the style sheet using the <link> tag inside the head section: <head> <link rel="stylesheet" type="text/css" href=“site_style.css" /> </head> • See style_sheets.html

  23. External Style Sheets • External style sheets enable you to change the appearance and layout of all the pages in your site by editing just one single CSS document. • They give a consistent look to the entire site. • Multiple external style sheets may be referenced inside a single HTML document. 

  24. External style sheet • Create a text file containing the style declarations. • File should have extension “.css” such as: mystyle.css • Link, or import that file to the HTML file using special tags in the header. <link href=“URL” rel=“stylesheet” type=“text/css”> mystyle.css OR @import or multiple LINK tags allow you to use more than one style sheet in the same document <style> @import url(“mystyle.css”)</style>

  25. Cascading Order • If a property has been set for the same selector in different style sheets, the value will be inherited from the more specific (innermost) style sheet.  • (next slide)

  26. Cascading Order • We say that all the styles will "cascade" into a new "virtual" style sheet by the following rules, where number four has the highest priority: • Browser default • External style sheet (.css file) • Internal style sheet (inside the <head>) • Inline style (inside an HTML element)

  27. Style Inheritance • If a style is not specified for an element, it inherits the style of its parent element; This is called style inheritance.

  28. CSS • http://www.w3schools.com/css/css_border.asp • http://www.w3schools.com/css/css_text.asp • http://www.w3schools.com/css/css_text.asp

  29. The id Selector • The style rule below will match any element that has an id attribute with a value of "green": #green {color: green} <h1 id="green">Some text</h1>

  30. The id Selector • The style rule below will match any p element that has an id attribute with a value of "green": p#green {color: green}

  31. The class Selector • 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>

  32. The class Selector • Omit the tag name in the selector to define a style that will be used by all elements that have that class: .center {text-align: center} • Both h1 and p have class="center". <h1 class="center"> center-aligned </h1> <p class="center"> also center-aligned. </p>

  33. The class selector • Define a class (in the header) by • giving it a name preceded by a period • adding the standard style definitions inside {} <style type=“txt/css”> .bright {font-weight:bold; color:red}</style> • Apply the class to any HTML tag <strong class=“bright”> text </strong><h1 class=“bright”> text </h1>

  34. The class Selector • With the class selector you can define different styles for the same type of HTML element: p.right {text-align: right} p.center {text-align: center}

  35. The class Selector • Use the class attribute in your HTML document: <p class="right"> This paragraph will be right-aligned. </p> <p class="center"> This paragraph will be center-aligned. </p>

  36. Hyperlink pseudo-class • a: link {style for never visited links} • a: visited {style for visited links} • a: active {style for link that is currently being clicked} • a: hover {style when the mouse cursor is hovering over the link} – rollover effect. • examples/css/link_rollover.html a:hover {color=red; text-transform:uppercase; font-weight=bold}

  37. The <div> tag • The <div> tag defines a division/section in a document. • <div> is an HTML tag (not CSS) • It does not format content • Browsers usually place a line break before and after the div element

  38. The <div> tag • It is like a generic block level tag • Use the <div> tag to group block elements. • You can assign a CLASS (or ID or STYLE or ONCLICK or ONMOUSEOVER etc).

  39. <div> This is some text <div style="color:#FF0000;"> <h4>This is a header in a div section</h4> <p>This is a paragraph in a div section</p> </div>

  40. The <span> tag • The <span> tag is used to mark (or group) inline elements like letters, words or phrases.

  41. The <span> tag <p> text1 <span style="color:#0000FF;"> text2</span> text3 </p> <p><span style="color:#00DD45;">4</span> </p> output????

  42. The <span> tag <p> text1 <span style="color:#0000FF;"> text2</span> text3</p> <p style="color:#00DD45;">4</p> styles.html