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.
CSS Content Goes Here
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.
<link rel="stylesheet" type="text/css"href="style.css" />
<style type="text/css"> @import url(Path To stylesheet.css) </style>
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.
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:
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
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. For more information on making your website accessible to all users please read Dive into accessibility
Swapping stylesheets is beneficial not only for users with disabilities, but also power users who are particular about how they read Web documents.
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.
Next Chapter: Chapter 2 - The CSS Syntax