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.
Internal Stylesheet
First we will explore the internal method. This way you are simply placing
the CSS code within the tags of each (X)HTML file you
want to style with the CSS. The format for this is shown in the example
below.
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.
External Stylesheet
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.
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.
Cascading Order
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.
Inline Styles
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, which is better?
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 & 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 option.
Users with Disabilities
The use of external style sheets also can benefit users that suffer from
disabilities. For instance, a user can turn off your stylesheet or substitute
one of there own to increase text size, change colors and so on.
Power Users
Swapping stylesheets is beneficial not only for users with disabilities, but
also power users who are particular about how they read Web
documents.
Browser Issues
You will discover as you delve farther into the world of CSS that all
browsers are not created equally, to say the least. CSS can and will
render differently in various browsers causing numerous headaches.
