CSS How To
When a browser reads a style sheet, it will format the document according to
the information in the style sheet.
Three Ways to Insert CSS
There are three ways of inserting a style sheet:External Style Sheet
An external style sheet is ideal when the style is applied to many pages. With an external style sheet, you can change the look of an entire Web site by changing just one file.Each page must include a link to the style sheet with the <link> tag. The <link> tag goes inside the head section:
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>
"myStyle.css":
hr {color: sienna;}
p {margin-left: 20px;}
body {background-image: url("images/background.gif");}
p {margin-left: 20px;}
body {background-image: url("images/background.gif");}
| 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 |
Internal Style Sheet
An internal style sheet should be used when a single document has a unique style. You define internal styles in the head section of an HTML page, inside the <style> tag, like this:
<head>
<style>
hr {color: sienna;}
p {margin-left: 20px;}
body {background-image: url("images/background.gif");}
</style>
</head>
<style>
hr {color: sienna;}
p {margin-left: 20px;}
body {background-image: url("images/background.gif");}
</style>
</head>
Inline Styles
An inline style loses many of the advantages of a style sheet (by mixing content with presentation). Use this method sparingly!To use inline styles, add the style attribute to the relevant tag. The style attribute can contain any CSS property. The example shows how to change the color and the left margin of a paragraph:
<p style="color:sienna;margin-left:20px;">This is a paragraph.</p>
Multiple Style Sheets
If some properties have been set for the same selector in different style sheets, the values will be inherited from the more specific style sheet.For example, assume that an external style sheet has the following properties for the h3 selector:
h3
{
color: red;
text-align: left;
font-size: 8pt;
}
color: red;
text-align: left;
font-size: 8pt;
}
h3
{
text-align: right;
font-size: 20pt;
}
text-align: right;
font-size: 20pt;
}
color: red;
text-align: right;
font-size: 20pt;
text-align: right;
font-size: 20pt;
Multiple Styles Will Cascade into One
Styles can be specified:Tip: Even multiple external style sheets can be referenced inside a single HTML document.
Cascading order
What style will be used when there is more than one style specified for an HTML element?Generally speaking we can say that all the styles will "cascade" into a new "virtual" style sheet by the following rules, where number four has the highest priority:
- Browser default
- External style sheet
- Internal style sheet (in the head section)
- Inline style (inside an HTML element)

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