Download What is CSS? Brief historical overview W3C

CSS
Presented by Chris Sanyk
CSS: Why take a class?
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Basic CSS is really, really easy to learn.
The language syntax is pretty straightforward.
Examples are everywhere. Just ViewSource.
The tools needed to develop CSS are free and
available on any computer.
All you need is a text editor, a web browser, and
a few good references.
CSS: Why take a class:
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Advanced CSS can be pretty hard.
Complex CSS can be hard to work with.
Dealing with browser inconsistencies can be a
pain.
Keeping up to date with CSS as it develops takes
effort as well as patience.
Why this class:
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Most classes I’ve seen or taken have focused on by-thebook basics. I find those are easy enough to pick up on
your own.
What people really need from a class on CSS is to
acquire “street smarts” so they can avoid the traps that
ordinarily are discovered and defeated through
experience.
Hopefully you’ll come out of this with a solid
understanding of fundamentals, how to do the basic
stuff effectively and efficiently, and maybe a few cool
tricks.
My Goals
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NOT to become known as “the CSS guy”
I have 3 goals for this class:
1.
2.
3.
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To help others learn CSS and enable them to work with it,
and encourage sharing of expertise.
To improve my own comfort and competence with CSS so
that I can grow.
To build a course foundation that can be re-used by any
competent instructor, and improved upon in successive
teachings, and potentially packaged and sold as a product.
What goals do you have?
Student/Audience
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Where are you at?
Silently assess yourself on a 0-4 scale…
Your Instructor
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Overall: 3
Basics: 4
CSS for HTML <form> elements: 2
Browser compatibility: 2
CSS positioning: 2
CSS 3: 1-2
Probably some people in the room know more. Let’s
collaborate on making the class better!
History
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Before CSS, HTML used a combination of
<elements> and attributes=“” for controlling
the presentation of a web page.
This was limited at best, and gave rise to really
messy ugly code.
The worst of it was HTML 3.2.
History
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HTML 4 (and XHTML 1), which has been
around since 1999, was a major cleanup of this
mess, and was very successful in many ways.
11 years later, we’re just on the cusp of HTML
5.
OK, maybe this is also a testament to the
slowness of W3C.
Much of HTML 4’s success is owed to the
success of CSS, especially CSS 2.1.
History
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Initially, HTML was all there was.
It handled both describing the structure of a
document, as well as how the document should
be presented.
Presentational aspects of early HTML were
fairly limited, both in terms of the effects that
could be achieved, and how they were applied to
a document element.
History
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Early 90’s:
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1993-94:
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HTML begins to see real use. NCSA Mosaic launches WWW
revolution. Birth of the modern internet.
1995:
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HTML started coming together in the early 90’s (IETF)
HTML 2
1996:
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CSS 1 becomes a W3C recommendation in 1996. It is fairly
basic and not widely supported by web browsers right away.
No one can use it in the real world.
History
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1997:
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HTML 3.2 becomes the first version of HTML to achieve
W3C recommendation status. Previously, HTML was just
developed by various people and groups.
HTML 3.2 mostly consolidated a bunch of proprietary
extensions to HTML that had been created by Netscape,
Microsoft, and others.
Because browsers don’t support CSS well, and because CSS 1
is so limited, a host of presentational HTML elements and
attributes are incorporated into the 3.2 spec, turning it into a
horrid mess. HTML 3.2 code is bloated, ugly, and hard to
read as content becomes buried in a mess of presentational
markup.
History
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1998:
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CSS 2 becomes W3C recommendation.
1999:
CSS 1 finally well-supported in the browser.
 Beginning of a long period of inconsistent,
incomplete support for CSS 2.0 in the browser…
and seemingly endless frustration for web
developers.
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History
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2003-04
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Browsers now have decent support for much of CSS 2, and
continue to improve.
As of 2008, no browser had fully supported the CSS 2.0
specification.
2009:
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As of 2009, W3C has only managed to advance CSS 2.1 to
“candidate recommendation” status.
Despite this, CSS 2.1 is the current dominant de-facto
“standard”, and has been reasonably well-supported by
browsers since around 2005-6.
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Sadly, well-supported does not mean “perfectly” or “completely.”
Today
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CSS 3 is emerging. Parts of it are already widely
supported by current versions of major browsers.
Unfortunately a fair amount of users out there
aren’t on the latest versions, so 2.1 is still your
best bet.
CSS 3 extends and builds on 2.1, so W3C should
hurry the hell up and finalize the 2.1
recommendation already.
WTF, W3C?
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W3C risks making itself irrelevant if they can’t release
recommendations more quickly.
WWW currently has a strong foundation in open
standards. This should not be taken for granted.
If these standards do not evolve to meet the needs of
web developers, we run the risk of losing this openness.
Proprietary innovation could overtake open standards.
WWW++ could end up being built from proprietary
tech such as Flash and Silverlight.
On the other hand…
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Getting 10 (well, OK, more like 5) years use out
of something is pretty nice.
Not having to learn the latest version every year
or so frees you from being stuck in the perpetual
learning curve, and allows you to get good.
Stability is great… but only if major problems
are solved and deficiencies get addressed.
CSS weak points
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Layout
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Flexible/fluid layout is difficult
Columns
Lacking Orthoganality (orthowha?)
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There’s often more than one way to achieve a desired effect, and getting
different properties to work together is… screwy.
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Position, Display, Float:
Font sizes and dimensional units.
Which do you use, when?
How do they work together?
Selectors are unable to ascend (there’s no “parent of ” selector.)
Vertical control (lack thereof, especially with centering).
No way to express calculated values.
No explicit scope declaration.
CSS weak points
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User agent settings can mess up your style (local
custom CSS, font settings, default colors, etc.)
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This is actually a not a weak point, as it means that ultimately
the client has control over their preferences. But this can
drive designers and product owners nuts because they don’t
have absolute control.
Even if the standards remain stable, if the browsers are
constantly going through updates and their support of
CSS changes over time, you’re shooting at a moving
target.
The Browser
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Browser Support for CSS
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Always lags behind W3C, at least for a while.
Sometimes differs from what W3C specifies. (Sometimes
browser devs make mistakes, sometimes W3C is vague.)
Some browsers also support proprietary CSS extensions (got
tired of waiting for slow W3C).
This is fine, insofar as W3C does not own CSS; that’s why
they’re called recommendations.
It does, however, inconvenience web developers when
browsers implement CSS support differently.
Each browser has a “default” stylesheet that it uses for
determining what plain HTML looks like. And each is
somewhat different.
Browser Support
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Bottom line: Browser support for CSS is
inconsistent.
If you’re unlucky, badly interpreted CSS can
cause your site to look broken in a particular
browser (usually IE).
It’s a pain to try to support every platform; it’s
sane to support open standards.
Try to stay sane.
You may not always be able to.
Browser Support
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Your website will therefore look slightly
different in different browsers.
Browsers ignore markup they don’t understand.
Browsers mangle markup they think they
understand.
Browsers attempt to render invalid markup, but
do so inconsistently.
HTML + CSS
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Stop using HTML attributes for controlling
presentational aspects of the web page.
Avoid using tables for layout. It’s possible,
though difficult, but worth it.
Accessibility (508 & WCAG)
 SEO
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Let HTML provide logical structure, and let CSS
handle presentation.
Why use CSS? Advantages of CSS
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In a word, reusability. CSS saves you work.
Declare a style rule once, apply it everywhere you
need to.
 Content from one page can be brought into another
without having to re-work the HTML. (In theory.)
 Reduce burden on web server by providing lightweight markup.
 Easier maintenance.
 HTML is more readable.
 Less work to make changes to the way the site looks.
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No, really. Why should I bother to
learn CSS?
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Do you really need to know CSS in order to make web
sites? Mmmm… maybe not.
Consider: do you want to be a codemonkey, or do you
want to author content?
CMS frameworks do a lot of monkey work for you.
They are good. Use them. Even if you’re a
codemonkey. Especially if you’re a codemonkey.
Use/modify existing templates/themes/etc.
Concentrate on your message, and having something
interesting to say.
Why learn CSS?
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Control.
Customization.
Do something unique.
You want to understand why the #@%* your
web site doesn’t look right in $browser, and fix
it.
Someone’s giving you money.
How to use CSS
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Connecting CSS to HTML
Linked stylesheets
 Embedded stylesheets
 Inline style declarations
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Linked Stylesheets
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<link rel="stylesheet" type="text/css"
href=“mystyle.css" />
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The preferred way. An external .css file contains
your CSS code, and can be referenced by
multiple HTML documents. Maximizes
reusability.
HTML document can reference multiple .css
files, and take on styling from each of them.
<link> goes in the <head> element.
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Embedded Stylesheets
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<style><!-/*your CSS here*/
--></style>
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Not very reusable, since the CSS rules can only be
utilized by the HTML document it is embedded within.
Useful in the event that you need to make sure the
HTML file stays with its CSS markup.
Devious “css injection” possibilities… (don’t allow
<style> tag in web forums, or users will do bad things
to your site.)
<style> is w3c-valid only in <head> but most browsers
will accept it in <body>
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Inline style attribute
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style=“declaration1; declaration2;”
<p style=“font-size:10pt; color:red;”>
Nearly any HTML element can take a style attribute
Inline styles are more specific; that is, they will override
rules declared in external or embedded stylesheets.
Inline styles are good for ad hoc or temporary
solutions, but at the expense of the re-usability of the
HTML/content. They’re fine for posting comments to
discussion boards.
CSS Syntax
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Selectors
Properties
Values
Comments
property:value = declaration.
; = separator.
Single declarations or the end
declarations don’t technically need ;
it is a separator, not a terminator.
Selector {property: value;}
/* Comment */
CSS Syntax
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Whitespace doesn’t matter
(with one important
exception.)
Format for readability, try to
be consistent.
CSS itself is not case
sensitive.
Treat it like it is anyway;
some browsers seem to
implement it as case sensitive,
and urls referencing
resources in CSS are case
sensitive.
p
{
font-size:10pt;
color: red;
}
div, p, h1 {fontfamily: arial;}
#head {backgroundimage:
url(/caseSentitiveurl-to/image.jpg);}
CSS Syntax: Selectors
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Universal
Named element
Class
ID
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*
div
.myclass
#MyID
Combinations
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Class and ID selectors can combine with elements to
make a more specific rule:
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p.myclass{} selects only <p class=“myclass”></p>
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Not <p></p>
Not <div class=“myclass”></div>
p#MyID{} selects only <p id=“MyID”></p>
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Not <p></p>
Not <div id=“MyID”></div>
CSS Syntax: Selectors (advanced)
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List of selectors
(comma)
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h1, .myclass,
.otherclass {}
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Descendent selector
(space)
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.myclass p {}
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Child selector
Sibling selector
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ul > li {}
h1 + p{}
Classes, IDs
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Use IDs for unique regions on page, since ID
value must be unique for the page.
Make ID and Class names semantic, not
descriptive. (e.g., .warning -- not .red )
CSS Selectors
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Pseudo-classes
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:link
:visited
:hover
:active
:focus
:first-child
CSS Selectors
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Pseudo-element
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:first-line
:first-character
:after
:before
CSS 2.1 Selector Summary
Pattern
Meaning
*
Matches any element.
E
Matches any E element (i.e., an element of type E).
E F
Matches any F element that is a descendant of an E element.
E > F
Matches any F element that is a child of an element E.
E:first-child
Matches element E when E is the first child of its parent.
E:link
E:visited
Matches element E if E is the source anchor of a hyperlink of which the target is not yet visited (:link) or already visited
(:visited).
E:active
E:hover
E:focus
Matches E during certain user actions.
E:lang(c)
Matches element of type E if it is in (human) language c (the document language specifies how language is determined).
E + F
Matches any F element immediately preceded by a sibling element E.
E[foo]
Matches any E element with the "foo" attribute set (whatever the value).
E[foo="warning
"]
Matches any E element whose "foo" attribute value is exactly equal to "warning".
E[foo~="warnin
g"]
Matches any E element whose "foo" attribute value is a list of space-separated values, one of which is exactly equal to
"warning".
E[lang|="en"]
Matches any E element whose "lang" attribute has a hyphen-separated list of values beginning (from the left) with "en".
DIV.warning
Language specific. (In HTML, the same as DIV[class~="warning"].)
E#myid
Matches any E element with ID equal to "myid".
Other CSS Fundamentals
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Font size and dimensional units
Colors
The Box Model
Font size WTF
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Proportional or Absolute?
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Each has pros and cons; there is no ideal perfect
method.
Proportional units are usually the way to go.
Absolute units are useful in some cases
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Absolute units: pt px in cm mm
Proportional units: ex em %
(print media)
Be careful/take advantage of nested proportional
sizing.
Colors
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Days of 216 “web safe” colors is long gone.
Descriptive color names
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System color names (OS-specific; maybe customized by user).
#xxxxxx; hex notation
#xxx;
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(shorthand, less precision, saves 3 bytes of bandwidth)
RGB(0-255,0-255,0-255) and RGB(0-100%,0-100%,0-100%)
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Only 16 color names are actually W3C standard.
+124 (for a total of 140) more color names (orig. Netscape) are widely supported.
But does each browser truly render them all identically? These can’t be relied
upon absolutely for all user agents; some may not support them at all.
(why bother?)
Seem to be popular in generated code for some reason.
If using number values, it can be helpful to comment with a name or
description of the color.
End user monitors are very likely not color calibrated, accuracy is not critical.
Colors
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“Transparent” named color
Transparency and elements
Background color
 Text
 Images
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Gradients
The Box Model
http://www.blogoff.es/2010/02/01/15-articulos-de-css-para-principiantes/
Positioning
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static (default)
relative (offset relative to static)
absolute (offset relative to first non-static
parent)
fixed – position in a fixed position within the
window viewpane. Does not scroll.
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IE support spotty. ( IE >= 7)
Float and Clear
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float and clear are not implemented consistently
among all leading browsers. This is why they are
sometimes more of a pain than they should be.
Blame IE for its bad behavior with float. Usually can
be fixed with an extra <div> to wrap the element and
float the <div>.
Floated elements do not influence the height of their
parent. Beware overflowing floats.
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Use 0-height <div> with Clear after a overflowing Floated
element if you need to fix it.
Float and Clear
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float:left or float:right takes the
element out of normal flow, and wraps other
content around it.
If the floated HTML element does not have a
defined width, float will not work properly
unless you provide a width value. (<p>,
<blockquote>, <div>, etc.) The floated
element’s width has to be narrower than its
parent.
Float and Clear
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clear tells the browser what to do with the
next element that comes after a floated element.
If an element clears, it will start on the next line,
not wrap around the floated element.
You can clear:left, clear:right, or
clear:both.
clear applies to the element occurring after a
floated element, not to the floated element.
Display vs. Visibility
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Be aware of distinction between display:none
and visibility:hidden.
Display:none collapses.
Visibility:hidden takes up space.
HTML De-<table>-fication
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<table> was always intended for tabular data.
Originally HTML had little/nothing else
available for laying out pages.
<table> was purposed for this.
<table> is reasonably easy to design and is
rendered consistently by browsers.
You don’t get weird bugs with table based
layouts like you will with a <div> based layout.
So why nix <table>?
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Return <table> to its intended purpose (yeah
but why?)
Allow machine readers (that’s Search Engines as
well as assistive reader technologies) to read the
page and interpret it correctly.
Improve your search result rankings as table
contents do not score as high in SEO as do
properly marked up page content.
Getting there
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If you’re still in a world of <table> based
layouts, you’re behind a few years.
If you’re a complete newbie and are just getting
the hang of HTML+CSS and aren’t doing
anything serious, use <table> layouts for a while
like training wheels.
Get used to using CSS to control all
presentational aspects and get good at that.
Worry about making “proper” layouts later.
Getting there
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When you’re ready to transition from table to
div layout…
Hopefully you’re using a framework or CMS
that does it for you already and you don’t have
to worry. Find a template or whatever and go!
If one does not exist exactly like what you want,
find one that’s close, and tweak it.
Getting there
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If not using a CMS or framework, work into it.
Start simple.
Re-do your layout iteratively.
Challenge yourself to use as FEW tables as possible.
(Most <table> layouts use NESTED tables. The more
nesting, the worse for accessibility.)
Work on eliminating the inner tables first.
Stick with fixed-width layouts until you’re really good.
Fluid layouts are harder & not necessarily better.
Using CSS Effectively…
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Selector Specificity
Select only what you want
 Use a container and descendant selectors
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Efficiency
 Re-usability
 Avoid “leaking” (being too general with a selector
declaration.)
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Learn the “Cascade” and take advantage of it.
Specificity and the Cascade
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Selector specificity:
http://www.blogoff.es/2010/02/01/15-articulos-de-css-para-principiantes/
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!important trumps all (except client overrides)
Conflicting rules:
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Top score wins.
Tie goes to last declared.
Rules that don’t conflict accumulate.
…And Efficiently
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Use lists of selectors to consolidate like blocks
code.
Use comments to explain what you’ve done and
why.
Common useful CSS
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CSS reset
#ID Regions with descendant selectors and
unstyled children
Font size: what type of units?
CSS Box model
Clever/Cool CSS
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Transparency
:hover effects
Positioning
Conditional rules
Dynamic CSS with Javascript
Combining multiple classes in one element.
CSS sprites
CSS3 Served fonts
CSS for other media
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Not just for the screen!
Printer – definitely use.
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Mobile Devices – maybe use.
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Get rid of the “printable view” link. Test by printing to PDF
or Print Preview; avoid wasting paper.
Hard to test for. Mobile devices vary widely, and most are
still bad.
Aural – for text-to-speech technologies.

Consider using, especially if you are concerned with
accessibility.
Tips
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Look at your site with CSS turned off.
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If it’s readable and the placement of stuff makes
sense, that’s a good sign that your HTML doesn’t
suck.
Be sure your HTML uses a doctype
declaration…
and complies with it.
Validate your HTML and your CSS.
Dealing with non-standard browser
behavior
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Should you?
If it breaks the site.
 If you’re being paid.
 If you’re a perfectionist.
 If you’re a masochist.
 Use web server stats to decide if it makes sense.

Understanding browser-specific
issues
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Accessibility/Usability
Cosmetic
If you have to address browserspecific problems…
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Try standards first.
If standards-compliant CSS is handled differently by
some browser… <cough>IE</cough>
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use a conditional stylesheet to handle it, rather than “one size
fits all” code.
Try to keep your browser-specific fixes short, isolated,
commented, and tidy.
Use tools to hone in on the problem.

See Useful Tools slide coming up
Handling for IE6
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Eric asked… “What to do in IE6 vs. everything else”
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Tie a rock to it and drop it off the continental shelf
Seriously, it’s 2010 FFS.
Serve a warning to the user that their browser is unsafe for web browsing
and recommend they upgrade use something else.
If you absolutely must support IE6 for some reason…
Make sure you have IE6 around to test with.
Use IE conditionals to attach an IE6-specific .css that overrides the
standard-compliant stuff if the user agent reports itself as IE6.
Use hacks as a last resort.

Many ways to do different stuff. Google for ideas. Come up with your own
if you can do better.
Recommended resources

The Web
W3Schools.com
 W3C.org
 www.css3.info
 www.d.umn.edu/itss/support/Training/Online/we
bdesign/css.html
 A slew of web developer blogs, YMMV. Google &
bookmark.

A few good articles and resources
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http://jontangerine.com/log/2007/09/theincredible-em-and-elastic-layouts-with-css
http://www.bigbaer.com/css_tutorials/css.imag
e.text.wrap.htm
http://www.bigbaer.com/css_tutorials/css.scale.
image.html.tutorial.htm
http://riddle.pl/emcalc/
http://matthewjamestaylor.com/blog/perfect-3column.htm
Recommended resources

Print
Web Design in a Nutshell 3rd Edition (O’Rielly)
 CSS pocket reference (O’Rielly)
 HTML Utopia: Designing Without Tables Using
CSS ISBN0-9752402-7-7
 CSS: The Missing Manual
 CSS: The Definitive Guide

Useful Tools

Mozilla
Web Developer Toolbar
 Firebug
 Validator extensions
 ColorZilla (color picker)
 MeasureIt (pixel ruler)

Useful Tools

Safari tools
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Chrome tools
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Suggest any
IE
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Suggest any
IE Developer Toolbar
Notepad++
Awe and Inspiration
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www.romancortes.com – Godlike CSS.
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Pure CSS portraits of George W. Bush, Homer
Simpson, other amazing CSS marvels.
Your site here! Do something extraordinary.
Homework
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Teach this class.
Improve this class.
Create reference examples of various CSS
properties and applications.
Make a web site.
Do something creative.
Bring in a tricky problem you’re stuck on and
get people to help you.