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HTML defines six levels of headings. A heading element implies all
the font changes, paragraph breaks before and after, and any white
space necessary to render the heading. The heading elements are H1, H2,
H3, H4, H5, and H6 with H1 being the highest (or most important) level
and H6 the least. For example:
<H1>This is a top level heading</H1> Here is some text.
<H2>Second level heading</H2> Here is some more text.
Use the DIV element together with header elements when you want to
make the hierarchical structure of a document explicit. This is needed
as header elements themselves only contain the text of the header, and
do not imply any structural division of documents into sections. Header
elements have the same content model as paragraphs, that is text and
character level markup, such as character emphasis, inline images, form
fields and math.
Headers play a related role to lists in structuring documents, and
it is common to number headers or to include a graphic that acts like a
bullet in lists. HTML 3.0 recognizes this with attributes that assist
with numbering headers and allow authors to specify a custom graphic.
The numbering style is controlled by the style sheet, e.g.
- The style sheet specifies whether headers are numbered, and
which style is used to render the current sequence number, e.g. arabic,
upper alpha, lower alpha, upper roman, lower roman or a numbering
scheme appropriate to the current language.
- Whether the parent numbering is inherited, e.g. "5.1.d" where 5 is
the current sequence number for H1 headers, 1 is the number for H2
headers and 4 for H3 headers.
The seqnum and skip attributes can be used to
override the default treatment of header sequence numbers, and provide
for a continuity with numbered lists.
The dingbat or src attribute may be used to
specify a bullet-like graphic to be placed adjacent to the header. The
positioning of this graphic is controlled by the style sheet. The
graphic is for decorative purposes only and silently ignored on
non-graphical HTML user agents.
User agents are free to wrap lines at whitespace characters so as to
ensure lines fit within the current window size. Use the
entity for the non-breaking space character, when you want
to make sure that a line isn't broken! Alternatively, use the NOWRAP
attribute to disable word wrapping and the <BR> element to force
line breaks where desired.
Netscape includes two tags: <NOBR>...</NOBR>, and
<WBR>. The former turns off wordwrapping between the start and
end NOBR tag, while WBR is for the rare case when you want to specify
where to break the line if needed. Should HTML 3.0 provide an
equivalent mechanism to WBR, (either a tag or an entity)?
- An SGML identifier used as the target for hypertext
links or for naming particular elements in associated style sheets.
Identifiers are NAME tokens and must be unique within the scope of the
- This is one of the ISO standard language abbreviations,
e.g. "en.uk" for the variation of English spoken in the United Kingdom.
It can be used by parsers to select language specific choices for
quotation marks, ligatures and hypenation rules etc. The language
attribute is composed from the two letter language code from ISO 639,
optionally followed by a period and a two letter country code from ISO
- This a space separated list of SGML NAME tokens and is
used to subclass tag names. For instance, <H2 CLASS=Section>
defines a level 2 header that acts as a section header. By convention,
the class names are interpreted hierarchically, with the most general
class on the left and the most specific on the right, where classes are
separated by a period. The CLASS attribute is most commonly used to
attach a different style to some element, but it is recommended that
where practical class names should be picked on the basis of the
element's semantics, as this will permit other uses, such as
restricting search through documents by matching on element class
names. The conventions for choosing class names are outside the scope
of this specification.
- Headings are usually rendered flush left. The ALIGN
attribute can be used to explicitly specify the horizontal
- The heading is rendered flush left (the
- The heading is centered.
- The heading is rendered flush right.
- Heading lines are justified where
practical, otherwise this gives the same effect as the default
<h1 align=center>This is a centered heading</H1>
Here is some text. <H2 align=right>and this is a flush right
heading</H2> Here is some more text.
- This attribute is common to all block-like elements. When
text flows around a figure or table in the margin, you sometimes want
to start an element like a header, paragraph or list below the figure
rather than alongside it. The CLEAR attribute allows you to move down
- move down until left margin is clear
- move down until right margin is clear
- move down until both margins are clear
Alternatively, you can decide to place the element alongside the
figure just so long as there is enough room. The minimum width needed
is specified as:
- clear="40 en"
- move down until there is at least 40 en units free
- clear="100 pixels"
- move down until there is at least 100 pixels
The style sheet (or browser defaults) may provide default minimum
widths for each class of block-like elements.
- A sequence number is associated with each level of
header from the top level (H1) to the bottom level (H6). This attribute
is used to set the sequence number associated with the header level of
the current element to a given number, e.g. SEQNUM=10. Normally, the
sequence number is initialized to 1 at the beginning of the document
and incremented after each header element. It is reset to 1 by any
header element of a higher level, e.g. an H1 header resets the sequence
numbers for H2 to H6. The style of header numbering is controlled by
the style sheet.
- Increments the sequence number before rendering the
element. It is used when headers have been left out of the sequence.
For instance, SKIP=3 advances the sequence number past 3 omitted items.
- Specifies an iconic image to appear preceding the
header. The icon is specified as an entity name. A list of standard
icon entity names for HTML 3.0 is given in an appendix of this
- Specifies an image to appear preceding the header. The
image is specified as a URI. This attribute may appear together with
the MD attribute.
- Specifies a message digest or cryptographic checksum for the
associated graphic specified by the SRC attribute. It is used when you
want to be sure that a linked object is indeed the same one that the
author intended, and hasn't been modified in any way. For instance,
MD="md5:jV2OfH+nnXHU8bnkPAad/mSQlTDZ", which specifies an MD5 checksum
encoded as a base64 character string. The MD attribute is generally
allowed for all elements which support URI based links.
- The NOWRAP attribute is used when you don't want the
browser to automatically wrap lines. You can then explicitly specify
line breaks in headings using the BR element. For example:
<h1 nowrap>This heading has wordwrap turned off<br>
and the BR element is used for explicit line breaks</H1>