External style sheet
When a style needs to be applied to many pages, the external style sheet is ideal. When using an external style sheet, you can change the appearance of the entire site by changing a file. Use the <link> label to link to the style sheet on each page. <Link> tag in (document) header:
<Head> <link
Rel = "stylesheet" type = "text/CSS" href ="mystyle.css
"/> </Head>
Internal style sheet
When a document requires a special style, you should use an internal style sheet. You can use the <style> label to define an internal style sheet in the Document Header, as shown in the following figure:
<style type="text/css"> hr {color: sienna;} p {margin-left: 20px;} body {background-image: url("images/back40.gif");}</style>
Inline Style
Because we need to mix the performance and content together, inline styles will lose many of the advantages of style sheets. Use this method with caution. For example, when a style only needs to be applied once on one element.
To use inline Styles, you must use the style attribute in the relevant labels. The style attribute can contain any CSS attribute. This example shows how to change the color and left margin of a paragraph:
<Pstyle
= "Color: Sienna; margin-left: 20px"> This is a paragraph </P>
Priority:
Inline> embedded> external reference
Thanks to http://www.howzhi.com/group/web-dev/discuss/11096's sharing.
External style? Inline style? Internal style sheets? Differences