When you are developing external style sheets your latest changes may not be
loaded when you reload a page. To force a reload that reloads all linked
files you press the CTRL or CLOVER key while clicking on the reload button.
Keyboard shortcuts: CTRL-F5 works for Chorme and Internet Explorer; CTRL-SHIFT-R (CLOVER-SHIFT_R)
for Firefox, and CTRL-R (CLOVER-R) works for both Safari and Chrome.
CSS syntax
A style sheet is a collection of zero or more named style elements.
StyleSheet ::= +[ StyleElement ];
Each style element has a selector followed by its definition.
StyleElement ::= Selector Definition;
A selector can be written in three primary ways.
Selector ::= ( element
-- Selects all instances of the HTML/XML element
,
.identifier
-- selects all elements with the attribute class="identifier"
,
#identifier
-- selects the one element with the attribute id="identifier", avoid its use
};
A definition is zero or more property-value pairs, all written within a pair
of braces. Note that property-value pairs are separated with a semicolon, ';'
but it is good policy to use it as a property-pair terminator.
A property-value pair is a property name that is defined by the world
wide web consortium (W3C), followed by a colon, ':' and followed by the value of the
property, the syntax of which depends upon the property being defined.
Items in blue are selectors.
Items in magenta are definitions.
body{
background-color: #FFFF88;
color: #000000; }li{ margin-top: .5em; }.alignHorizontalCenter{
width: 50%;
margin-left: auto;
margin-right: auto; }.academicHonesty{
width: 50%;
margin-left: auto;
margin-right: auto;
font-size: 1.5em; }.fixedFont{ font-family: Georgia, "Times New Roman", serif; }/* Why can this be a list?
Why is Times New Roman in quotes? */#lastUpdated{
font-style: italic;
font-weight: bold;
color: red; }#font13{
font-size: 1.3em;
font-weight: bold; }
Style sheet location
Inline style
Property-value pairs are entered as a style attribute of the element and
affect only that instance of element. An example is shown in the
following.
<p style="color: blue; font-size: 1.5em">Bigger font in blue</p>
Bigger font in blue
Embedded style
A style sheet can be defined within the page it is being used. You do this
only if the style elements are needed only on the one page. The style sheet
elements are typed within the style element and the style element
should only be written as a part of the head element, as shown in
the following example.
A style sheet can also be stored in a file with the extension css. You
use this option if the style elements are going to be used on more than one
page. In this case the style sheet is referenced with link element that
is a part of a head element, as in the following example.
An external style sheet can be imported into an embedded style or an
external style with the @import directive
CSS semantics
The way in which the style name is written determines how the style is used.
identifer
If a style name is the name of an HTML element, then the style
is applied to every instance of that element.
.identifier
If the style name is a class selector, then the style can be referenced
in any HTML element. For example, <table class=fixedFont>
You can also use class="fixedFont indent"
to use two style definitions, here
fixedFont and
indent
#identifier
If the style is an id selector, then the style is meant to be
referenced only once in only one HTML element in the page. For example,
<table id=font13>WARNING: DO NOT USE ID SELECTOR For a discussion of why you should avoid id selectors visit
http://csswizardry.com/2011/09/when-using-ids-can-be-a-pain-in-the-class
CSS comments
You can write comments in a a style sheet using the block comment characters '/*',
start comment, and '*/', end comment that are used in C and Java, as in the
following example.
… style text /* comment text
can span lines*/
more style text …
The rules of precedence mean that the definition most local or closest to the displayed
data take precedence over definitions further from the displayed data.
Cascade example — Remove style definitions close to the text and see
the changes that take place.
Inheritance
Some styles are inherited from the parent element. For example, fonts, font size.
Some are not inherited. For example, margins and padding.
Inheritance is indicated by using the keyword inherit as a property value.
color: inherit
Use of reset.css
The goal of a reset stylesheet is to
reduce browser inconsistencies in things like default line heights, margins
and font sizes of headings, and so on.