There are two ways of identifying some of your page content as having been quoted from some other source. These two alternative methods are the <blockquote> and <q> tags.
<blockquote>This is a block quote.</blockquote>
<q>This is a quote.</q>
How quotes identified by either of these tags actually displays on your web page if you haven't taken control of it using stylesheet commands depends on which web browser is being used. The only thing that can be said for certain about how the code will display is that all current browsers are configured to indent blockquotes relative to the surrounding text. Depending on which browser is being used quotes identified using the <q> tag may also be indented, may be enclosed within quotation marks, or in some cases no special formatting is applied and the browser relies entirely on your stylesheet to define how the quotes should be displayed.
One thing not to do with blockquote tags is to use them for indentation. The tags should only be used to define quotes and you should use the appropriate stylesheet commands to set appropriate margins when you require text that is not a quote to be indented.
One attribute that can be optionally entered into either of these tags is the cite atrtribute. If specified then the value assigned to the attribute should be a reference either to the web page being quoted or should contain the ISBN of the book that the quote comes from. None of the current browsers actually do anything with this attribute and so the quote will not behave any differently when the attribute is included than it does without.
This article written by Stephen Chapman, Felgall Pty Ltd.