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How To Add CSS

When a browser reads a style sheet, it will format the HTML document according to the information in the style sheet.

Three Ways to Insert CSS​

There are three ways of inserting a style sheet:

  • Inline CSS
  • Internal CSS
  • External CSS

Inline CSS​

An inline style may be used to apply a unique style for a single element.

To use inline styles, add the style attribute to the relevant element. The style attribute can contain any CSS property.

Example: Inline styles are defined within the "style" attribute of the relevant element:

<!DOCTYPE html>  
<html>  
	<body>  
		<h1 style="color:blue;text-align:center;">This is a heading</h1>  
		<p style="color:red;">This is a paragraph.</p>  
	</body>  
</html>
note

An inline style loses many of the advantages of a style sheet (by mixing content with presentation). Use this method sparingly.

Internal CSS​

An internal style sheet may be used if one single HTML page has a unique style.

The internal style is defined inside the <style> element, inside the head section.

Example: Internal styles are defined within the <style> element, inside the <head> section of an HTML page:

<!DOCTYPE html>  
<html>  
	<head>  
		<style>  
			body {  
				background-color: linen;  
			}  
			  
			h1 {  
				color: maroon;  
				margin-left: 40px;  
			}  
		</style>  
	</head>  
	<body>  
		<h1>This is a heading</h1>  
		<p>This is a paragraph.</p>  
	</body>  
</html>

External CSS​

With an external style sheet, you can change the look of an entire website by changing just one file!

Each HTML page must include a reference to the external style sheet file inside the <link> element, inside the head section.

Example: External styles are defined within the <link> element, inside the <head> section of an HTML page:

<!DOCTYPE html>  
<html>  
	<head>  
		<link rel="stylesheet" href="mystyle.css">  
	</head>  
	<body>  
		<h1>This is a heading</h1>  
		<p>This is a paragraph.</p>  
	</body>  
</html>

An external style sheet can be written in any text editor, and must be saved with a .css extension.

The external .css file should not contain any HTML tags.

Here is how the "mystyle.css" file looks:

body {  
	background-color: lightblue;  
}  
  
h1 {  
	color: navy;  
	margin-left: 20px;  
}
note

Do not add a space between the property value and the unit (such as margin-left: 20 px;).

The correct way is: margin-left: 20px;

Multiple Style Sheets​

If some properties have been defined for the same selector (element) in different style sheets, the value from the last read style sheet will be used.

Assume that an external style sheet has the following style for the <h1> element:

h1 {  
	color: navy;  
}

Then, assume that an internal style sheet also has the following style for the <h1> element:

h1 {  
	color: orange;  
}

Example: If the internal style is defined after the link to the external style sheet, the <h1> elements will be "orange":

<head>  
	<link rel="stylesheet" type="text/css" href="mystyle.css">  
	<style>  
		h1 {  
			color: orange;  
		}  
	</style>  
</head>

Example: However, if the internal style is defined before the link to the external style sheet, the <h1> elements will be "navy":

<head>  
	<style>  
		h1 {  
			color: orange;  
		}
	</style>  
	<link rel="stylesheet" type="text/css" href="mystyle.css">  
</head>

Cascading Order​

What style will be used when there is more than one style specified for an HTML element?

All the styles in a page will "cascade" into a new "virtual" style sheet by the following rules, where number one has the highest priority:

  1. Inline style (inside an HTML element)
  2. External and internal style sheets (in the head section)
  3. Browser default

So, an inline style has the highest priority, and will override external and internal styles and browser defaults.

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