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Cascading Style Sheets: Basics
I450 Technology Seminar Copyright 2003, Matt Hottell
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What is CSS? A set of rules for displaying markup content
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What is CSS? A set of rules for displaying markup content Cascading:
Display rules “cascade” down The most specific rule is used
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What is CSS? A set of rules for displaying markup content Cascading:
Display rules “cascade” down The most specific rule is used Styles Sheet: Rules are created as styles
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The Need for CSS Fixing kludges in HTML
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The Need for CSS Fixing kludges in HTML
Separation of content and display
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The Need for CSS Fixing kludges in HTML
Separation of content and display More options for displaying content
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The Need for CSS Fixing kludges in HTML
Separation of content and display More options for displaying content Efficiency
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CSS Example
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Visual Display in HTML <h1><font color=‘red’ face=“Georgia, Times New Roman, Times, serif”> This will be a heading 1 in red Georgia font</font></h1> Every time I want my text to look the same, I have to retype or cut and paste all of this markup</font></h1>
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Style Rules CSS style rules look like this: Selector {
property0:value0; property1:value1; propertyZ:valueZ }
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CSS Reference
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Inline Style Sheet Using a Style Attribute
<h1 style=“color:red; font-family: Georgia, Times New Roman, Times, serif”> This also shows up as heading 1 in red Georgia font. I don’t have to use the font tag any more. </h1> However, I still have to retype or cut and paste the markup every time I want to use the same style.</h1> Notice that we switch from the attribute “face” for the “font” element to the property “font-family” in CSS. Names of attributes in HTML do not necessarily exactly match the names of properties in style rules.
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Inline Style Sheet Using a Style Attribute In-Class exercise:
Create an inline stylesheet that makes all paragraph text black, centered, and 12 pixels in size.
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Inline Style Sheet In-Class exercise:
Create an inline stylesheet that makes all paragraph text black, centered, and 12 pixels in size. <html> <head><title>black, centered, 12px text</title></head> <body> <p style=“color:black; text-align:center; font-size:12px”> This is black, 12px, centered text.</p> </body> </html>
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Embedded Style Sheet Using a Style Element <html>
<head><title>Embedded style sheet</title> <style type=“text/css”> h1 {color:red; font-family: Georgia, Times New Roman, Times, serif;} </style> </head><body> <h1>This will also appear as a heading 1 in red Georgia font. In the head of this document, I declared an embedded style sheet that will make all h1 tags in this document red with Georgia font</h1> <p>But how do I make some h1 tags use this style and others look different? </p>
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Embedded Style Sheet Using a Style Element In-Class exercise:
Create an embedded stylesheet that makes all paragraph text blue, background-color #777777, and 14 pixels in size.
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Embedded Style Sheet Using a Style Element In-Class exercise:
Create an embedded stylesheet that makes all paragraph text blue, background-color #777777, and 14 pixels in size. <html> <head><title>Embedded style sheet</title> <style type=“text/css”> p {color:blue; background-color:#777777; font-size:14px;} </style> </head><body> <p>This should be blue with gray background and size 14</p> </body></html>
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Class Selectors <html>
<head><title>Embedded style sheet</title> <style type=“text/css”> .red {color:red; font-family: Georgia, Times New Roman, Times, serif;} </style> </head><body> <h1 class=“red”>This will also appear as a heading 1 in red Georgia font. In the inline style sheet I declared a generic class style that applies red Georgia to ANY element declared as class red. I simply change a value in the style element in the head and all elements using that style will change to match</h1> <p class=“red”> This will also be in red Georgia font. Now I can be very specific when I apply styles, but I still have to add the same markup in the HEAD to each of my pages. How do I make all my pages use the same styles without copying markup to each page? </p>
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Linked Style Sheets <html>
<head><title>Linked style sheet</title> <link rel=“stylesheet” type=“text/css” href=“mystyle.css”> </head><body> <h1 class=“red”>This will also appear as a heading 1 in red Georgia font. In the head of this document I declared a link to an outside stylesheet named “mystyle.css”. In that external stylesheet I place all of the style declarations I was using in my inline stylesheet</h1> <p> Now I can change the way all of my pages display simply by modifying a value in my single external stylesheet. How efficient! </p>
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Example External Stylesheet
h1.redH1 { color:red; font-family: Georgia, Times New Roman, Times, serif } body { background-color: #333333; .blueback { background-color: blue; color: white p { font-size: 12px; text-align: center;
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Linked Style Sheet Using an External Stylesheet In-Class exercise:
Create an external stylesheet that defines a new style named phunky that makes text pink, centered, and bold. The sheet should also make the background color of the page ”antiquewhite”
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Linked Style Sheet Using an External Stylesheet In-Class exercise:
Create an external stylesheet that defines a new style named phunky that makes text pink, centered, and bold. The sheet should also make the background color of the page ”antiquewhite” .phunky { color:pink; text-align: center; font-weight: bold; } body{ background-color: antiquewhite
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Cascading revisited When using multiple styles that conflict, which will be displayed?
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Cascading revisited When using multiple styles that conflict, which will be displayed? Order: Inline style sheet Embedded style sheet External style sheet Browser default
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Style Rule Values Colors: Names for some: Hexadecimal RGB RGB%
blue, red, green, pink Hexadecimal #0000FF, #FF0000, #00FF00, #FF3399 RGB rgb(0,0,255), rgb(255,0,0), rgb(0,255,0) RGB% rgb(0%,0%,100%), rgb(100%,0%,0%)
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Style Rule Values Font size: px for pixels (a dot on the screen)
pt for point (1/72 of an inch) font-size: 12pt pc for pica (12 points) font-size: 2pc
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Modifying Hyperlinks We can modify the way hyperlinks appear by creating style rules modifying the <a> tag with the following “pseudo-classes”: link visited hover active
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Modifying Hyperlinks a:link {color:#0000ff} a:visited {color: #00ff00}
a:hover {color:fuschia; font-weight:bold} a:active {font-size:30pt} Order here is important!
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Modifying Hyperlinks You can also combine a class selector with a pseudo-class: a.outsidelink:link {color:#0000ff} a.insidelink:visited {color: #00ff00} a.fun:hover {color:fuschia; font-weight:bold}
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Span and Div <span> and <div> are tags that let you select a group of elements and apply styles to them <span> is an inline tag no breaks are added before or after <span></span> <div> is a block tag a break is usually added by the browser before and after the <div></div> tags
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Span and Div <html>
<head><title>Span and Div</title> <style type=“text/css”> .red {color:red; font-family: Georgia; font-weight:bold;} </style> </head><body> <p>This will also appear as normal paragraph text except <span class=“red”>here because I made the text red,bold, and Georgia font without breaking up the paragraph.</span> Now I am back to normal... </p> <p> I start off as normal paragraph text here as well. However, when I use a div tag to apply a style, my paragraph is broken like <div class=“red”>this. You can see that the browser sets off this text from the text before and </div> after it. Now I am back to normal again. </p> </body></html>
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Putting it all together
In-class exercise: Create a web page with an external style sheet that does the following: All paragraph text is white with a blue background and centered. All links get bigger and change colors when hovered over Background color is “aliceblue” Creates a style “redstyle” that makes text 16px red Garamond. All h1 text is centered and underlined.
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