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It’s All About Style. The Basics of Style Sheets Presented by Barry Diehl. Overview. What are Style Sheets? Benefits of CSS Problems with CSS Recommendations Sources. What are style sheets?.
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It’s All About Style The Basics of Style Sheets Presented by Barry Diehl
Overview • What are Style Sheets? • Benefits of CSS • Problems with CSS • Recommendations • Sources
What are style sheets? • A collection of rules that determines how a browser displays HTML tags. Also known as Cascading Style Sheets (CSS). • Consists of two parts: • Selector – the HTML tag the style will affect • Style – has a property and a value
Inline Styles – Add to a tag • No selector • Applies to the tag in which it belongs <P style=“font-size: 18 pt”>Paragraph text here</P> • Best used as an exception to regular rules
Inline Styles - <SPAN> tag • Define an area over which a style will be applied • Not attached to a structural HTML element <SPAN style=“margin-left: 1in”> <H2>Heading</H2> <P>Paragraph text.</P> </SPAN>
Internal Styles • Applies to entire document • Insert <STYLE> tag between <HEAD> tags <HEAD> <TITLE>Page Title</TITLE> <STYLE TYPE=“text/css”> BODY {background: white; color: black} H1 {font: 24 pt “Arial” bold} P {font: 12 pt “Arial”; text-indent: 0.5in} </STYLE> </HEAD>
External Style Sheet • Style data are kept in a separate file <HEAD> <TITLE>External Style Example</TITLE> <LINK REL=STYLESHEET HREF=“global.css” TYPE=“text/css”> </HEAD> • <STYLE> is not in the file
Comparison – Inline Styles • Useful for setting styles for small sections of a document • Can override all other style specification methods • Combining style with content and structural information • Doesn’t apply to same tag elsewhere in document or other documents
Comparison – Internal Styles • Useful for setting styles for an entire document • Can use classes to create styles for multiple types of tags • Style information is included when the document downloads for faster rendering • Cannot be used for multiple documents
Comparison – External Style Sheet • Standardize styles for a site • Can use classes to create styles for multiple types of tags • If used repeatedly, will be cached for faster retrieval • Requires extra time to download a separate file • Documents may not render correctly if there’s an error with the style sheet file • Hard to make small changes in the document
Defining Styles with CLASS • Add styles to a specific tag <STYLE TYPE=“text/css”> BODY {background: white; color: black; font-size: 14pt} P.large {font-size: 18pt} P.small {font-size: 10pt} </STYLE> <P CLASS=“large”>This paragraph will be large.</P> <P CLASS=“small”>This paragraph will be small.</P> • Add styles without a tag – just have a period before the class name
Handling Exceptions with ID • Assign exception value to an id using the # sign • Use the id to change a value in a style <STYLE TYPE=“text/css”> .normal {font-size: 16; color: blue} #fire {color: red} </STYLE> <P CLASS=“normal”>Normal text is 16-point blue.</P> <P CLASS=“normal” ID=“fire”>This text is 16-point red.</P>
Inheritance • Styles are inherited from previous definitions of tags <STYLE TYPE=“text/css”> BODY {background: white; color: black; font-size: 12pt} H1 {font-size: 24pt; color: green} UL {font-size: 10pt; font-style: italic} </STYLE>
Cascading • Collecting, sorting and applying rules • A rule’s importance is based on: • If it has an explicit weight (“!important”) • Where the rule originated • Designer • User • Browser • How specific the rule is • Order of presentation (recent has priority)
Benefits of CSS • Standardize pages across a web site • Save bandwidth/load faster • Develop faster • Change pages quickly and easily • Easy to learn and use • Separates presentation and content
Problems with CSS • Browser implementation varies – until 6.0, Netscape was the worst • Style sheets won’t allow pages to be identical on all screens – there are too many variables
Recommendations • 86% of Internet users surf with Internet Explorer • Determine percentage for your own site • Use pixels – only safe method – points are good only for printing • Use style sheets for what they do well – like fonts. Use tables for margins. • Pages should be viewable without style sheet • See browser compatibility table at: www.webreview.com/style/css1/charts/mastergrid.shtml
XSL • New language designed to work with XML • Can’t be used with HTML
Sources HTML Publishing on the Internet, 2nd edition by Brent Heslop and David Holzgang (The Coriolis Group, 1998) Webmonkey (Mulder’s Stylesheets Tutorial) http://hotwired.lycos.com/webmonkey/authoring/tutorials/tutorial1.html Sample Sheets from W3C – www.w3c.org/StyleSheets/Core/Overview Jeffrey Zeldman – www.zeldman.com Little Shop of CSS Horrors – www.haughey.com/csshorrors