When a browser reads a style sheet, it will format the document according to the information in the style sheet.
There are three ways of inserting a 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:
An external style sheet can be written in any text editor. The file should not contain any html tags. The style sheet file must be saved with a .css extension. An example of a style sheet file called "myStyle.css", is shown below:
|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;|
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:
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 h1 element:
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 <h1> element:
then, assume that an internal style sheet also has the following property for the <h1> element:
If the page with the internal style sheet also links to the external style sheet the properties for the <h1> element will be:
The left margin is inherited from the external style sheet and the color is replaced by the internal style sheet.
Styles can be specified:
Tip: Even multiple external style sheets can be referenced inside a single HTML document.
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:
So, an inline style (inside an HTML element) has the highest priority, which means that it will override a style defined inside the <head> tag, or in an external style sheet, or in a browser (a default value).
|Note: If the link to the external style sheet is placed after the internal style sheet in HTML <head>, the external style sheet will override the internal style sheet!|