Styling the New Web
Web Usability with Style Sheets
A CHI 2003 Tutorial
Steven Pemberton
CWI and W3C
Kruislaan 413
1098 SJ Amsterdam
The Netherlands
Steven.Pemberton@cwi.nl
www.cwi.nl/~steven
Agenda
The day is split into four blocks, each of 90 minutes.
Each block consists of about 45 minutes lecture, followed by 45 minutes
practical.
The breaks between blocks are 30 minutes, with 90 minutes for lunch.
Introduction, basic CSS: selectors, fonts, colours.
Break
Intermediate level: advanced selectors, inheritance, margins, borders,
padding.
Lunch
Advanced: text properties, background, positioning, cascading.
Break
The Future: XML and XHTML.
About the Instructor
Steven Pemberton is a researcher at the CWI, The Centre for Mathematics
and Computer Science, a nationally-funded research centre in Amsterdam, The
Netherlands, the first non-military Internet site in Europe.
Steven's research is in interaction, and how the underlying software
architecture can support the user. At the end of the 80's he built a
style-sheet based hypertext system called Views.
Steven has been involved with the World Wide Web since the beginning. He
organised two workshops at the first World Wide Web Conference in 1994,
chaired the first W3C Style Sheets workshop, and the first W3C
Internationalisation workshop. He was a member of the CSS Working Group from
its start, and is a long-time member (now chair) of the HTML Working Group,
and co-chair of the XForms Working Group. He is co-author of (amongst other
things) HTML 4, CSS, XHTML and XForms.
Steven is also Editor-in-Chief of ACM/interactions.
Objectives
HTML has for too long, and incorrectly, been seen as a purely presentation
language. It was originally designed as a structure description language, but
extra elements were added later by browser manufacturers in order to
influence the presentation. This has had the effect of limiting Web site
usability by introducing presentation elements that slow down Web access,
reduce or prevent accessibility to the sight-impaired, limit the sorts of
devices that may be used to view websites, and reduce the end-user's options
when viewing a document.
The World Wide Web Consortium (W3C) started the Style Sheet activity in
1995 in order to get HTML back to its pure form. The result of this was
Cascading Style Sheets (CSS), which allows the separation of content and
presentation in Web sites.
Using style sheets has many benefits, including:
- Separation of content and presentation means that Web pages are easier
to write.
- Since images are no longer needed to represent styled text, Web pages
download significantly faster.
- By separating out the presentation elements, blind and other
sight-impaired users are able to access the Web much more easily,
especially since CSS explicitely supports aural browsers.
- By allowing style sheets to specify sizes in relation to other sizes,
rather than as absolute sizes, people with reduced sight can scale pages
up and still see them as they were intended.
- By not coding device-dependent presentations in the HTML pages are
viewable on a wider range of devices.
- You can now design the look of your site in one place, so that if you
change your house style, you only need to change one file to update your
entire site.
Even if the Web remained based on HTML, these would be enough reasons to
use style sheets. However, the Web is now going in a new direction: XML, and
XML has no inherent presentation semantics at all. To use XML you
have to use a style sheet to make your site visible.
As a part of the movement to XML, a new version of HTML, called XHTML, is
being developed. Since all presentation-oriented elements are being dropped,
style sheets will become essential there too.
So the objectives of this course are to give an advanced introduction to
the use of CSS to style HTML and XML documents, showing in passing how this
can improve usability, and to give an introduction to the use of XML and
XHTML.
CSS level 1 will be presented, since this is the version currently widely
implemented, with pointers to what is in CSS 2, and what can be expected in
CSS 3.
These notes have been produced entirely in XHTML and CSS, using different
stylesheets for printing, screen use, and presentation. In particular, there
are only three images used (to demonstrate the use of images): a star, and
two versions of a flower. All other things that look like images are in fact
just styled with CSS.
It should go without saying that to properly appreciate this document, you
have to view it with a browser with good CSS support.
If you can see this text, your browser apparently does not
support CSS.
Course Plan
- 9:00-10:30
- Introduction, basic CSS: selectors, fonts, colours; Practical
- 11:00-12:30
- Intermediate-level stuff: advanced selectors, inheritance, margins,
borders, padding; Practical
- 2:00-3:30
- Advanced stuff: text properties, background, positioning;
Practical
- 4:00-5:30
- The Future: XML and XHTML; Practical
CSS
- CSS is a language that allows you to specify how a document, or set of
documents, should look.
- Advantages:
- Separates content from presentation
- Makes HTML a structure language again
- Makes HTML easier to write (and read)
- All HTML styles (and more) are possible
- You can define a house style in one file
- Accessible for the sight-impaired
- You can still see the page on non-CSS browsers
- CSS is also an enabling technology for XML
Separating Content and Presentation: Author Advantages
- Easier to write your documents
- Easier to change your documents
- Easy to change the look of your documents
- Access to professional designs
- Your documents are smaller
- Visible on more devices
- Visible to more people
Separating Content and Presentation: Webmaster Advantages
- Separation of concerns
- Simpler HTML, less training
- Cheaper to produce, easier to manage
- Easy to change house style
- Documents are smaller: less bandwidth
- Reach more people
- Search engines find your stuff easier
- Visible on more devices
Separating Content and Presentation: Reader Advantages
- Faster download (one of the top 4 reasons for liking a site)
- Easier to find information
- You can actually read the information if you are sight-impaired
- Information more accessible
- You can use more devices
Separating Content and Presentation: Implementor Advantages
- Improves the implementation (separation of concerns)
- Can produce smaller browsers
Levels
- CSS has been designed with upwards and downwards compatibility in mind.
- CSS1: basic formatting, fonts, colours, layout; quick and easy to
implement
- CSS2: more advanced formatting; aural style sheets
- CSS3: printing, multi-column, ...
- In general a valid CSS1 style sheet is also a valid CSS2 style
sheet.
- In general a CSS2 style sheet can be read and used by a CSS1-supporting
browser.
Check your log files!
- More than 95% of surfers now use a CSS1-compatible browser:
- Microsoft IE 3, 4, 5, 6
- Netscape 4, 6, 7 and its Mozilla-based relatives
- Opera 3.5, 4, 5, 6, 7
- While the quality of the support for CSS on these browsers varies,
though is continually improving, you never need to use the <FONT>
tag again!
- Today we'll be largely talking about CSS1, since it is widely
implemented
Why is Usability Important for Websites?
Forrester did research among 8000+ users on why they chose one website
above another equivalent one. Reasons were:
- Content 75%
- Usability 66%
- Speed 58%
- Freshness 54%
All other reasons were 14% or lower.
CSS can't help you with Content or Freshness, but it can with the other
two!
Why is CSS good for usability?
- Presentation is not hard-wired in the HTML
- Users can make their own choices (font size, colours, etc), and
override the documents
- Pages load faster
- Pages become more accessible for the sight-impaired (who can use speech
browsers)
- Pages are viewable on a wider range of platform types
Warning about old browsers
CSS implementations are now quite good, but older browsers had a variety
of mistakes. Unfortunately, some browser manufacturers want to offer
backwards compatibility with those buggy old browsers. So they have two
modes: compliant mode, and legacy mode.
To decide which mode to use they look at the document.
Legacy and compliant modes
So if you want your CSS to work right, always include a
DOCTYPE at the head of your document.
Box model
- All elements have this box model.
- The margin's colour is transparent
- The border's colour is by default the same as the text of the content,
but can be set separately
- The padding has the same colour as the background colour of the
content
height and width properties
| Margin |
|
|
Border |
|
|
|
|
Padding |
|
|
|
|
|
|
Content |
|
|
|
Height |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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Width |
|
|
|
|
- The 'height' and 'width' properties of an element affect the height and
width of the 'content' part
- So if you set width to 4em, padding to 3em, border to 2em, and margin
to 1em, the whole box will be (4 + 2×3 + 2×2 + 2×1) = 15em wide. (But
see note later on 'auto' values).
Use of margins
- Use margins for indenting:
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sed diam nonumy eirmod.
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dolor sit.
Invidunt ut labore et dolore magna aliquyam erat, sed
diam voluptua.
- exdenting (using negative margins):
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sed diam nonumy eirmod.
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rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum
dolor sit.
Invidunt ut labore et dolore magna aliquyam erat, sed
diam voluptua.
- adding space between paragraphs
- etc.
When vertical margins meet
When two margins meet vertically, only the larger is used (so the gap
between a heading and the following paragraph is the larger of the heading's
margin-bottom and the paragraph's margin-top)
An Example
When two margins meet vertically, only the larger is used
(so the gap between a heading and the following paragraph is the larger of
the heading's margin-bottom and the paragraph's
margin-top)
An Example
When two margins meet vertically, only the larger is used
(so the gap between a heading and the following paragraph is the larger of
the heading's margin-bottom and the paragraph's
margin-top)
Example of padding
blockquote
{ margin: 2em;
background-color: yellow;
padding: 2em
}
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy
eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam
voluptua.
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eirmod tempor invidunt ut labore.
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gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
Usage of borders
Use borders for:
- Setting off text with a line each side
- Enclosing text in a box
- Putting a line under a paragraph
- Marking changed paragraphs with a line
A border will often be too close to the text: use padding to set it off
from the text:
The End The
End
text-indent
- This specifies the indentation of the first line of a block of text
- Example values: 0, 4em, 1%, ...
- Initial: 0
- Use negative values for exdenting a line.
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elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna
aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores
et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem
ipsum dolor sit amet.
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elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna
aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores
et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem
ipsum dolor sit amet.
background-repeat
- Specifies how background image is to be displayed
- Values: repeat, no-repeat, repeat-x, repeat-y
- no-repeat: just once at start position
- repeat-x: repeat horizontally both sides of the start position
- repeat-y: repeat vertically above and below start position
- repeat: repeat in all directions (tile the element)
- Initial: repeat
Float
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*** 
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amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut
labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et
accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea
takimata sanctus est Lorem ipsum dolor sit.
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy
eirmod tempor invidunt ut labore et dolore magna aliquyam erat, no sea
takimata sanctus est Lorem ipsum dolor sit amet.
*** Lorem ipsum dolor sit amet,
consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore
et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et
justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata
sanctus est Lorem ipsum dolor sit.
Use of float
- Float works on any type of element, even text blocks!
- It can replace the use of tables for some layout
p.menu {float: left;
background-color: yellow;
...
<p class="menu">Menu items ...</p>
<p>Text ...</p>
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eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam
voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita
kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
Float for multi-columns
div.col {
width: 31%;
text-align: justify;
padding-left: 1%;
padding-right: 1%;
border-left: solid 1px black;
margin: 1em 0;
float: left;
}
div.col.first {border-style: none}
An example of columns
Here is an example of columns using CSS:
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sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore
magna.
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sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore
magna.
This is a div of class = "col". Lorem ipsum dolor sit amet, consetetur
sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore
magna.
And then back to single column format after the
divs.
Implementation
Already available in:
- Microsoft IE 3, 4, 5, 6
- Netscape 4, 6, 7
- Opera 3, 4, 5, 6, 7
- X-Smiles
- NetClue
- OmniWeb
- Mozilla, Galeon, Konqueror, Phoenix, K-Meleon, Chimera, ...
Implementation
- Escape
- Icab
- Openwave for phones
- Nokia phones
- Ericsson phones
- Arachne
- Emacs-w3
- Amaya
- Athena
- Closure
- HP ChaiFarer
- ICE