Chapter 1 : Introduction to CSS
A CSS (cascading style
sheet) file allows you to separate your web sites (X)HTML content from it’s
style. As always you use your (X)HTML file to arrange the content, but all of
the presentation (fonts, colors, background, borders, text formatting, link
effects & so on…) are accomplished within a CSS.
At this point you have
some choices of how to use the CSS, either internally or externally.
First we will explore
the internal method. This way you are simply placing the CSS code within the
<head></head> tags of each (X)HTML file you want to style with the
CSS. The format for this is shown in the example below.
<head>
<title><title>
<style type=”text/css”>
CSS Content Goes Here
</style>
</head>
<body>
<title><title>
<style type=”text/css”>
CSS Content Goes Here
</style>
</head>
<body>
With this method each
(X)HTML file contains the CSS code needed to style the page. Meaning that any
changes you want to make to one page, will have to be made to all. This method
can be good if you need to style only one page, or if you want different pages
to have varying styles.
Next we will explore
the external method. An external CSS file can be created with any text or HTML
editor such as “Notepad” or “Dreamweaver”. A CSS file contains no (X)HTML, only
CSS. You simply save it with the .css file extension. You can link to the file
externally by placing one of the following links in the head section of every
(X)HTML file you want to style with the CSS file.
<link rel=”stylesheet” type=”text/css” href=“Path To
stylesheet.css” />
Or you can also use
the @import method as shown below
<style type=”text/css”>@import url(Path To stylesheet.css)</style>
Either of these
methods are achieved by placing one or the other in the head section as shown
in example below.
<head>
<title><title>
<link rel=”stylesheet” type=”text/css”href=”style.css” />
</head>
<body>
<title><title>
<link rel=”stylesheet” type=”text/css”href=”style.css” />
</head>
<body>
or
<head>
<title><title>
<style type=”text/css”> @import url(Path To stylesheet.css)</style>
</head>
<body>
<title><title>
<style type=”text/css”> @import url(Path To stylesheet.css)</style>
</head>
<body>
By using an external
style sheet, all of your (X)HTML files link to one CSS file in order to style
the pages. This means, that if you need to alter the design of all your pages,
you only need to edit one .css file to make global changes to your entire
website.
Here are a few reasons
this is better.
·
Easier Maintenance
·
Reduced File Size
·
Reduced Bandwidth
·
Improved Flexibility
Are you getting the idea? It’s really cool.
In the previous
paragraphs, I have explained how to link to a css file either internally or
externally. If you understood, than I am doing a good job. If not don’t fret,
there is a long way to go before we are finished. Assuming you have caught on
already, you are probably asking, well can I do both? The answer is yes. You
can have both internal, external, and now wait a minute a third way? Yes inline
styles also.
I have not mentioned
them until now because in a way they defeat the purpose of using CSS in the
first place. Inline styles are defined right in the (X)HTML file along side the
element you want to style. See example below.
<p style=”color: #ff0000;”>Some red text</p>
Some red text
Inline styles will NOT
allow the user to change styles of elements or text formatted this way
So with all these
various ways of inserting CSS into your (X)HTML files, you may now be asking
well which is better, and if I use more than one method, in what order do these
different ways load into my browser?
All the various
methods will cascade into a new “pseudo” stylesheet in the following order:
1. Inline Style (inside (X)HTML element)
2. Internal Style Sheet (inside the <head>
tag)
3. External Style Sheet
As far as which way is
better, it depends on what you want to do. If you have only one file to style
then placing it within the <head></head> tags (internal) will work
fine. Though if you are planning on styling multiple files then the external
file method is the way to go.
Choosing between the
<link related=> & the @import methods are completely up to you. I
will mention that the @import method may take a second longer to read the CSS
file in Internet Explorer than the <link related=> option. To combat this
see Flash of unstyled
content
Chapter 2 : CSS Syntax
The syntax for CSS is
different than that of (X)HTML markup. Though it is not too confusing, once you
take a look at it. It consists of only 3 parts.
selector { property:
value }
The selector is the
(X)HTML element that you want to style. The property is the actual property
title, and the value is the style you apply to that property.
Each selector can have
multiple properties, and each property within that selector can have
independent values. The property and value are separated with a colon and
contained within curly brackets. Multiple properties are separated by a semi
colon. Multiple values within a property are sperated by commas, and if an
individual value contains more than one word you surround it with quotation
marks. As shown below.
body {
background: #eeeeee;
font-family: “Trebuchet MS”, Verdana, Arial, serif;
}
background: #eeeeee;
font-family: “Trebuchet MS”, Verdana, Arial, serif;
}
As you can see in the
above code I have separated the color from the font-family with a semi-colon,
separated the various fonts with commas and contained the “Trebuchet MS” within
quotations marks. The final result sets the body color to light grey, and sets
the font to ones that most users will have installed on there computer.
I have changed the way
I layout my code, but you can arrange it in one line if you choose. I find that
it is more readable if I spread each property to a separate line, with a 2 space
indention.
Inheritance
When you nest one
element inside another, the nested element will inherit the properties assigned
to the containing element. Unless you modify the inner elements values
independently.
For example, a font
declared in the body will be inherited by all text in the file no matter the
containing element, unless you declare another font for a specific nested
element.
body {font-family:
Verdana, serif;}
Now all text within
the (X)HTML file will be set to Verdana.
If you wanted to style
certain text with another font, like an h1 or a paragraph then you could do the
following.
h1 {font-family: Georgia, sans-serif;}
p {font-family: Tahoma, serif;}
p {font-family: Tahoma, serif;}
Now all <h1>
tags within the file will be set to Georgia and all <p> tags are set to
Tahoma, leaving text within other elements unchanged from the body declaration
of Verdana.
There are instances
where nested elements do not inherit the containing elements properties.
For example, if the
body margin is set to 20 pixels, the other elements within the file will not
inherit the body margin by default.
body {margin: 20px;}
Combining Selectors
You can combine
elements within one selector in the following fashion.
h1, h2, h3, h4, h5, h6 {
color: #009900;
font-family: Georgia, sans-serif;
}
color: #009900;
font-family: Georgia, sans-serif;
}
As you can see in the
above code, I have grouped all the header elements into one selector. Each one
is separated by a comma. The final result of the above code sets all headers to
green and to the specified font. If the user does not have the first font I
declared it will go to another sans-serif font the user has installed on their
computer.
Comment tags
Comments can be used
to explain why you added certain selectors within your css file. So as to help
others who may see your file, or to help you remember what you we’re thinking
at a later date. You can add comments that will be ignored by browsers in the
following manner.
/* This is a comment
*/
You will note that it
begins with a / (forward slash) and than an * (asterisks) then the comment,
then the closing tag which is just backward from the opening tag * (asterisks)
then the / (forward slash).
Chapter
3 : CSS Classes
The class selector
allows you to style items within the same (X)HTML element differently. Similiar
to what I mentioned in the introduction about inline styles. Except with
classes the style can be overwritten by changing out stylesheets. You can use
the same class selector again and again within an (X)HTML file.
To put it more simply,
this sentence you are reading is defined in my CSS file with the following.
p {
font-size: small;
color: #333333
}
font-size: small;
color: #333333
}
Pretty simple, but
lets say that I wanted to change the word “sentence” to green bold text, while
leaving the rest of the sentence untouched. I would do the following to my
(X)HTML file.
<p>
To put it more simply, this <span class=”greenboldtext”>sentence</span> you are reading is styled in my CSS file by the following.
</p>
To put it more simply, this <span class=”greenboldtext”>sentence</span> you are reading is styled in my CSS file by the following.
</p>
Then in my CSS file I
would add this style selector:
.greenboldtext{
font-size: small;
color: #008080;
font-weight: bold;
}
font-size: small;
color: #008080;
font-weight: bold;
}
The final result would
look like the following:
To put it more simply,
this sentence you are reading is styled in my CSS file by the following.
Please note that a
class selector begins with a (.) period. The reason I
named it “greenboldtext” is for example purposes, you can name it whatever you
want. Though I do encourage you to use selector names that are descriptive. You
can reuse the “greenboldtext” class as many times as you want.
Chapter
4 : CSS IDs
IDs are similar to classes, except once a specific id has been declared
it cannot be used again within the same (X)HTML file.
I generally use IDs to
style the layout elements of a page that will only be needed once, whereas I
use classes to style text and such that may be declared
multiple times.
The main container for
this page is defined by the following.
<div id=”container”>
Everything within my document is inside this division.
</div>
Everything within my document is inside this division.
</div>
I have chosen the id
selector for the “container” division over a class, because I only need to use
it one time within this file.
Then in my CSS file I
have the following:
#container{
width: 80%;
margin: auto;
padding: 20px;
border: 1px solid #666;
background: #ffffff;
}
width: 80%;
margin: auto;
padding: 20px;
border: 1px solid #666;
background: #ffffff;
}
You will notice that
the id selector begins with a (#) number sign instead
of a (.) period, as the class
selector does.
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