Level 0 / Level 1 / Level 2 / Level 3 / Netscape Mozilla / Microsoft Internet Explorer

Level 0 HTML Summary

An HTML document consists of text and tags that mark the structure of the document. Elements in an HTML document are delimited by the tags which include < and >. Some elements have both a start and end tag: e.g., <TITLE> and </TITLE>. Other elements use only a single tag: e.g., (the paragraph element). Some elements have attributes, which are qualifications of the element's meaning or optional parameters for that element.

A Level 0 HTML document can include the following elements with the attributes shown. In this document, the elements are listed in all capital letters (e.g., TITLE), and the attributes are indicated by initial capital letters (e.g., Href). In order to benefit from the information in this document, view both its HTML source (http://www.december.com/html/spec/level0.html) as well as its rendered form in a Web browser. The elements and entities are explained in the list below as well as demonstrated here in appropriate locations (e.g, HEAD elements are demonstrated only in the HEAD of this document; and I don't demonstrate the heading (H1...H6) within the list of elements).

Note that the different brands of browsers vary in how they render these features. The intent of HTML is that the browser designers have specified at each level of HTML a "basic set" of features that they should implement, so that their browser renders these HTML constructs some satisfactory way.

HTML Structure and Comment Elements

HTML: The HTML element identifies the file as containing HTML elements. Only HEAD, BODY, and comment elements that should go inside the HTML element start and stop tag.
comment: Comments can be included anywhere within an HTML document; comments can cross several lines of text:

Document Type Declaration: A document type declaration can be placed at the start of a an HTML document (before the opening <HTML> tag which identifies it as a document conforming to a particular version and level of HTML. For example:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Level 0//EN">
identifies this document as conforming to the specification of Level 0 HTML.

The HEAD and Related Elements

HEAD: The HEAD element brackets a set of unordered descriptive information about a document. Elements within the HEAD element include: TITLE, BASE, ISINDEX, and NEXTID.

TITLE: Every HTML must have one title element which identifies the contents of the document. The title may not contain anchors, paragraph elements, or highlighting. Choose a title which is descriptive outside the context of the document's creation, as the title is commonly used to identify a document in navigation and indexing applications (e.g., hotlists and spiders).
BASE: The BASE element can be used to record the URL of the original version of a document when the source file is transported elsewhere; the base element has one attribute, Href, which is used to define the base URL of the document. Partial URLs in the document are resolved by using this base address as the start of the URL.
ISINDEX: This element marks the document as searchable--the server on which the document is located must have a search engine defined that supports this searching.
LINK: this element is used to define a relationship between the document and other objects or documents. For example, a link element can indicate authorship or indicate the tree structure of a document.
The LINK element has the same attributes as the Anchor (A) element: Attributes:
- Href: this identifies the document or part of a document to which this link refers
- Name: this is a way to name this LINK as a possible destination for another hypertext document
- Rel: describes the relationship defined by this LINK, according to the possible relationships as defined by the HTML Registration Authority's list of relationships. For example, the value "made" for Rel indicates that current document (in which the Rev="made" statement is placed) is the creator of the document referenced in the Href attribute.
- Rev: Similar to Rel, above, but the Rev attribute indicates the reverse relationship as Rel. For Example, the LINK with Rev="made" indicates that the Href refers to who "made" the current document. This is commonly done to indicate authorship of a document.
- Urn: This indicates the Uniform Resource Name of the document; the specification for URN and other addressing is still in development.
- Title: This attribute is not to be used as a substitute for the TITLE attribute of the document itself, but as a title for the document given by the Href attribute of the LINK element. This attribute is rarely used or supported by browsers, but may have value for cross referencing the relationships the LINK element defines.
- Methods: This attribute describes the HTTP methods the object referred to by the Href of the LINK element supports. For example, one method is searching; a browser could thus use this Methods attribute to give information to the user about the document defined by the LINK element.
META: This element is used to identify meta-information (information about information) in the document. This element is not meant to take the place of elements which already have a purpose, for example the TITLE element, but to identify other information useful for parsing.
Attributes (see the header of this document for typical examples):
- Http-equiv: This attribute connects this META element to a particular protocol response which is generated by the HTTP server hosting the document. For example, you can use a redirect technique to automatically "send" a user from one URL to another.
 The key line in the HEAD element is (this takes you right back here):
 
 <META Http-equiv="refresh" Content="3; Url=../spec/level0.html#redirect">
- Name: This attribute is a name for the information in the document--not the title of the document (which should be defined in the TITLE element) but a "meta name" classifying this information.
- Content: A "meta name" for the content associated with the given name (defined by the Name attribute) or the response defined in Http-equiv.
NEXTID: This element is used by text generated software in creating identifiers; its attribute, N, is used to define the next identifier to be allocated by the text generator program. Normally, human writers of HTML don't use this element; and Web browsers ignore this element.

The BODY and Related Elements

BODY: The BODY element's start and stop tags mark the content of an HTML document.
A: this is the anchor element which is used as the basis for linking documents together.
Attributes:
- Href: this attribute identifies the URL of the hypertext reference for this anchor in the form Href="URL", where the URL given will be the resource which the browser retrieves when the user clicks on the anchor's hotspot. For example:
 W3C
 will take the user to the World Wide Web's home.
- Name: this attribute creates a name for an anchor; this name can then be used within the document or outside of the document in anchor to refer to the portion of text identified by the name. For example:
 Text can have a named anchor.
 A jump can go to that anchor from a point within the file in which it is named...
 ...or you can jump to an anchor from another file (perhaps on a remote host).
- Title: This attribute is for the title of the document given by the Href attribute of the anchor. A browser could use this information to display this title before retrieving it, or to provide a title for the Href document when it is retrieved (e.g., if the document is at a Ftp site, it will not have a title defined).
- Rel: Defines the relationship defined from the current document to the target (Href document). See the discussion of the Rel attribute in the LINK element, above.
- Rev: Defines the relationship defined from the target (Href document) to the current document. See the discussion of the Rev attribute in the LINK element, above.
- Urn: This indicates the Uniform Resource Name of the target (Href) document; the specification for URN and other addressing is still in development.
- Methods: Provides information about the functions the user can perform on the Href object. Similar to described above for Title, this information might be useful for the browser to display in advance.
Note that an anchor can have both the Name and Href attributes:

<A Name="W3C-reference" Href="http://www.w3.org/"<W3C>/A> 
character blocks: these are elements that help "chunk" text in lists or blocks.
- PRE: this element sets up a block of text which will be presented in a fixed-width font, with spaces as significant.
```
 PRE's one attribute, Width, can be used to specify the width of the 
 presentation. Anchors and 
 character formatting within PRE, but not elements that 
 define paragraph breaks (e.g., headings, address, the P element, etc).
 
```
- BLOCKQUOTE: this brackets text that is an extended quotation from another source.
 A typical rendering of a BLOCKQUOTE is to provide extra indentation on both sides, and possibly highlight the characters in the BLOCKQUOTE.
- UL (LI): The UL element:
 - Brackets an unordered list of items.
 - Employs the LI element to mark the elements.
 - Is rendered using bullets to start items.
 - Can have the Compact attribute to suggest to the Web browser to keep the items in the list close together: <UL Compact>
- OL (LI): The OL element:
 1. Brackets an ordered list of items.
 2. Employs the LI element to mark the elements.
 3. Is rendered using a numerical sequence.
 4. Can have the Compact attribute as the start of the list: <OL Compact>.
- MENU (LI): The MENU element:
 Brackets an more compact unordered list of items.
 Employs the LI element to mark the elements.
 Is rendered using bullets to start items.
 Can have the Compact attribute, as the start of the menu, <MENU Compact>.
- DIR (LI): The DIR element: brackets a list of items which are at most 20 characters wide. The intent is that a browser can render this in columns of 24 characters wide. DIR can use the Compact attribute as the start of the list, <DIR Compact>.
 ITEM A.
 ITEM B.
 ITEM C.
 ITEM D.
- DL (DT, DD): A definition list, or glossary has these parts:
 
 A term:
 a detailed explanation of a term.
 Another term:
 an explanation of a term, which may include several lines of text.
 Can have the Compact attribute.
 Use the Compact attribute <DL Compact> as the start of the list.
- ADDRESS: this element brackets ownership or authorship information, typically at the start or end of a document.
headers: H1, H2, H3, H4, H5, H6: these are elements that create an information hierarchy in a document.
separators
- HR: Horizontal rule, divides sections of text.
- P: this element signals a paragraph start; optionally, it can have a stop tag, .
spacing
- BR: This element forces a linebreak.
 Typically, this is used to represent postal addresses or text
 (like poetry) where linebreaks are significant. For example:
```
The HTML Institute 
45 General Square 
Markup, LA 70462 
 
```
 Is rendered as:
 The HTML Institute
 45 General Square
 Markup, LA 70462
images (IMG): The IMG element allows graphical browsers to place graphic images a document at the location of the element tag (to create an "inline image"). For example:
<IMG Src="http://www.december.com/html/images/icon.gif" Alt="HTML Station LOGO" Align="middle">
is rendered as:
Attributes:
- Src: This attribute indicates the source file of the image.
- Alt: a string of characters can be defined that will be displayed in non-graphical browsers. Non-graphical browsers otherwise ignore the IMG element.
- Align: this attribute sets the positioning relationship between the graphic and the text that follows it; values include:
 - top: the text following the graphic should be aligned with the top of the graphic.
 - middle: the text following the graphic should be aligned with the middle of the graphic.
 - bottom: the text following the graphic should be aligned with the bottom of the graphic.
- Ismap: this attribute identifies the image as an image map, where regions of the graphic are mapped to defined URLs. Hooking up these relationships requires knowledge of setting an image map file on the server to define these connections.
character sets
1. ASCII characters: an HTML document can, of course, contain all the keyboard characters such as a-z, A-Z, 0-1, and !@#$%^&*()_+-=|\{}[]:"~;'`<>?,./
2. Entities: since some characters (e.g., < > & ") are used within HTML to create tags, so some browsers don't render them; special entities can be used within documents to represent these characters:
 1. Less than sign (<)code is <
 2. Greater than (>) sign code is >
 3. Ampersand (&) code is &
 4. Double quote sign (") code is "
3. Iso-latin1: an HTML document can have the set of ISO Latin character entities; See ISO Latin 1 character entities (Table).
4. Numeric characters: use numeric codes can be used to represent characters; See Numeric code references in HTML (Table).

References

HTML materials from W3C

John December (john@december.com) / 03 Jun 1996