Paragraphs

A paragraph (from the Greek paragraphos, "to write beside" or "written beside") is a self-contained unit of a discourse in writing dealing with a particular point or idea. The start of a paragraph is indicated by beginning on a new line. Sometimes the first line is indented; sometimes it is indented without beginning a new line. At various times the beginning of a paragraph has been indicated by the pilcrow: ¶.

A paragraph typically consists of a unifying main point, thought, or idea accompanied by supporting details. The non-fiction paragraph usually begins with the general and moves towards the more specific so as to advance an argument or point of view. Each paragraph builds on what came before and lays the ground or run the length of multiple pages, and may consist of one or many sentences. When dialogue is being quoted in fiction, a new paragraph is used each time the person being quoted changed.

Indenting
Some styles do not indent the first paragraph, but do indent all those that subsequently follow. This follows the logic that the purpose of indenting is to separate paragraphs in a way that lets the reader know where one paragraph finishes and another begins. The general American practice is to indicate all paragraphs including the first, by indenting the first line (three to five spaces), whereas business letters generally use blank lines and no indent (these are sometimes known as "block paragraphs"). For other purposes indented paragraphs are preferred. Most published books use a device to separate certain paragraphs further when there is a change of scene or time. This extra space, especially when co-occurring at a page break, may contain an asterisk, three asterisks, a special stylistic dingbat, or a special symbol known as an asterism.

Details
In literature, a "detail" is a small piece of information within a paragraph. A detail usually exists to support or explain a main idea. In the following excerpt from Dr. Samuel Johnson's Lives of the English Poets, the first sentence is the main idea, that Joseph Addison is a skilled "describer of life and manners". The succeeding sentences are details that support and explain the main idea in a specific way.

"As a describer of life and manners, he must be allowed to stand perhaps the first of the first rank. His humour, which, as Steele observes, is peculiar to himself, is so happily diffused as to give the grace of novelty to domestic scenes and daily occurrences. He never 'o'ersteps the modesty of nature,' nor raises merriment or wonder by the violation of truth. His figures neither divert by distortion nor amaze by aggravation. He copies life with so much fidelity that he can be hardly said to invent; yet his exhibitions have an air so much original, that it is difficult to suppose them not merely the product of imagination."

Body paragraph

 * Begin with a topic sentence which states the main point of the paragraph.
 * Give supporting details to support that main point.
 * Conclude with a closing sentence which restates the main point.

Paragraphs in HTML
In XHTML, the p element marks a block of text as a paragraph - the opening tag  marks the beginning of a paragraph, and the closing tag   marks the end of a paragraph. The end tag is optional for legacy HTML, as the browser automatically starts another paragraph at the next  tag, or the next block element.

