Elementary Taxonomy | WebReference

Elementary Taxonomy

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Elementary Taxonomy

To ease understanding of HTML, elements are grouped in certain categories. One of these categories we have already looked at: Document head elements. These elements can only exist within the HEAD element.

The rest of the elements in HTML (except for HTML, HEAD and BODY) must be contained inside the BODY element. These are also grouped into two categories: block elements and inline elements.

P is an example of a block element. Block elements define a block of text or information. They are usually rendered as separate from other block elements (like paragraphs, that are traditionally rendered as a block of text with a top and bottom margin).

A, the anchor element, is an example of an inline element. Inline elements usually make sense even when they contain only part of a sentence or phrase. Inline elements are always contained within block elements.

There are two more distinctions that we can make: some elements can contain elements of the same type as themselves. We have already seen that paragraphs cannot contain other paragraphs. Other elements may contain elements of the same type, however. In this case, we say that the element can be nested. Also, there is a handful of elements that can be used either as inline elements or as block elements. We won't look at any of these in this tutorial, but it's useful to mention here. I'll explain how these are used once we get to see them in action.

As mentioned in the introduction to this tutorial, I won't cover every attribute of the elements that will be introduced. Some attributes are common to many elements and have special functions (such as controlling presentation or the language of the element), and I will teach you about these attributes in future tutorials, because they deserve the attention. But because I want these descriptions to be complete, I will mention the attributes without explaining them.

Let's have a look at the global structure elements first. Here's the description of the HTML element, the parent of all elements.

NameHTML
UsageThe top-level element; all other elements must be contained within this element
ContextCannot be contained within another element.
ContentsMust contain exactly one HEAD and one BODY element.
Start-tagOptional
End-tagOptional
Attributes:
language attributes

The HEAD element, that contains the document head.

NameHEAD
UsageThe document head, containing information about the document
ContextMust be contained inside an HTML element.
ContentsMust contain exactly one TITLE element and may contain any number of other head elements.
Start-tagOptional
End-tagOptional
Attributes:
language attributes
PROFILEURIMetadate profile dictionary

And the BODY element, that contains everything else.

NameBODY
UsageThe document body.
ContextMust be contained inside an HTML element.
ContentsMay contain any number of block elements.
Start-tagOptional
End-tagOptional
Attributes:
element identifiers
element title
style directives
event handlers
language attributes
color & background attributes

Now let's go on and take a look at the head elements.

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URL: http://www.webreference.com/html/tutorial3/2.html
Created: June 25, 1998
Revised: June 25, 1998