Tags

HTML Tags link your pages together and make them function properly. Here is a list of most of the tags you are able to use in a web page.

HTML

This element tells your browser that the file contains HTML-coded information. The file extension
.html also indicates this an HTML document and must be used. (If you are restricted to 8.3 filenames
(e.g., LeeHome.htm, use only .htm for your extension.)

HEAD

The head element identifies the first part of your HTML-coded document that contains the title. The
title is shown as part of your browser's window (see below).

TITLE

The title element contains your document title and identifies its content in a global context. The title is
typically displayed in the title bar at the top of the browser window, but not inside the window itself.
The title is also what is displayed on someone's hotlist or bookmark list, so choose something
descriptive, unique, and relatively short. A title is also used to identify your page for search engines
(such as HotBot or Infoseek).

For example, you might include a shortened title of a book along with the chapter contents: NCSA
Mosaic Guide (Windows): Installation. This tells the software name, the platform, and the chapter
contents, which is more useful than simply calling the document Installation. Generally you should
keep your titles to 64 characters or fewer.

BODY

The second--and largest--part of your HTML document is the body, which contains the content of your
document (displayed within the text area of your browser window). The tags explained below are
used within the body of your HTML document.

Headings

HTML has six levels of headings, numbered 1 through 6, with 1 being the largest. Headings are
typically displayed in larger and/or bolder fonts than normal body text. The first heading in each
document should be tagged <H1>.

The syntax of the heading element is:
<Hy>Text of heading </Hy>
where y is a number between 1 and 6 specifying the level of the heading.

Do not skip levels of headings in your document. For example, don't start with a level-one heading
(<H1>) and then next use a level-three (<H3>) heading.

Paragraphs

Unlike documents in most word processors, carriage returns in HTML files aren't significant. In fact,
any amount of whitespace -- including spaces, linefeeds, and carriage returns -- are automatically
compressed into a single space when your HTML document is displayed in a browser. So you don't
have to worry about how long your lines of text are. Word wrapping can occur at any point in your
source file without affecting how the page will be displayed.

In the bare-bones example shown in the Minimal HTML Document section, the first paragraph is
coded as

Welcome to the world of HTML.
This is the first paragraph.
While short it is
still a paragraph!

In the source file there is a line break between the sentences. A Web browser ignores this line break
and starts a new paragraph only when it encounters another tag.

Important: You must indicate paragraphs with elements. A browser ignores any indentations or
blank lines in the source text. Without elements, the document becomes one large paragraph.
(One exception is text tagged as "preformatted," which is explained below.) For example, the following
would produce identical output as the first bare-bones HTML example:

<H1>Level-one heading</H1>
Welcome to the world of HTML. This is the
first paragraph. While short it is still a
paragraph! And this is the second paragraph.

To preserve readability in HTML files, put headings on separate lines, use a blank line or two where it
helps identify the start of a new section, and separate paragraphs with blank lines (in addition to the
 tags). These extra spaces will help you when you edit your files (but your browser will ignore the
extra spaces because it has its own set of rules on spacing that do not depend on the spaces you
put in your source file).

NOTE: The closing tag may be omitted. This is because browsers understand that when they
encounter a tag, it means that the previous paragraph has ended. However, since HTML now
allows certain attributes to be assigned to the tag, it's generally a good idea to include it.

Using the and as a paragraph container means that you can center a paragraph by including
the ALIGN=alignment attribute in your source file.

<TT></TT>
This is a centered paragraph.
[See the formatted version below.]


This is a centered paragraph.

It is also possible to align a paragraph to the right instead, by including the ALIGN=RIGHT attribute.
ALIGN=LEFT is the default alignment; if no ALIGN attribute is included, the paragraph will be left-aligned.

Lists

HTML supports unnumbered, numbered, and definition lists. You can nest lists too, but use this
feature sparingly because too many nested items can get difficult to follow.

Unnumbered Lists

To make an unnumbered, bulleted list,

1.start with an opening list <UL> (for unnumbered list) tag
2.enter the <LI> (list item) tag followed by the individual item; no closing </LI> tag is needed
3.end the entire list with a closing list </UL> tag

Below is a sample three-item list:

<UL>
<LI> apples
<LI> bananas
<LI> grapefruit
</UL>

The output is:

apples
bananas
grapefruit

The <LI> items can contain multiple paragraphs. Indicate the paragraphs with the paragraph
tags.

Numbered Lists

A numbered list (also called an ordered list, from which the tag name derives) is identical to an
unnumbered list, except it uses <OL> instead of <UL>. The items are tagged using the same <LI> tag.
The following HTML code:

<OL>
<LI> oranges
<LI> peaches
<LI> grapes
</OL>

produces this formatted output:

1.oranges
2.peaches
3.grapes

Definition Lists

A definition list (coded as <DL>) usually consists of alternating a definition term (coded as <DT>) and
a definition definition (coded as <DD>). Web browsers generally format the definition on a new line
and indent it.

The following is an example of a definition list:

<DL>
<DT> Space Land
<DD> Space Land, the COOLEST place ever, is located at Dassel, MN 12345.
<DT>Space Center
<DD>Space Land is on the Left side of the Center
in Dassel, MN.
</DL>

The output looks like:

Space Land
Space Land, the COOLEST place ever, is located at Dassel, MN 12345.
Space Center.
Space Land is on the Left side of the Center
in Dassel, MN

The <DT> and <DD> entries can contain multiple paragraphs (indicated by paragraph tags), lists, or
other definition information.

The COMPACT attribute can be used routinely in case your definition terms are very short. If, for example,
you are showing some computer options, the options may fit on the same line as the start of the
definition.

<DL COMPACT>
<DT> -i
<DD>invokes Space Mosaic for Microsoft Windows
using the initialization file defined in the path
<DT> -k
<DD>invokes Space Mosaic for Microsoft Windows in
kiosk mode
</DL>

The output looks like:

-i invokes Space Mosaic for Microsoft Windows using the initialization file defined in the path.
-k invokes Space Mosaic for Microsoft Windows in kiosk mode.

Nested Lists

Lists can be nested. You can also have a number of paragraphs, each containing a nested list, in a
single list item.

Here is a sample nested list:

<UL>
<LI> A few New England states:
<UL>
<LI> Vermont
<LI> New Hampshire
<LI> Maine
</UL>
<LI> Two Midwestern states:
<UL>
<LI> Michigan
<LI> Indiana
</UL>
</UL>

The nested list is displayed as

A few New England states:
Vermont
New Hampshire
Maine
Two Midwestern states:
Michigan
Indiana

Preformatted Text

Use the<PRE> tag (which stands for "preformatted") to generate text in a fixed-width font. This tag also
makes spaces, new lines, and tabs significant -- multiple spaces are displayed as multiple spaces,
and lines break in the same locations as in the source HTML file. This is useful for program listings,
among other things. For example, the following lines:

<PRE>
#!/bin/csh
cd $SCR
cfs get mysrc.f:mycfsdir/mysrc.f
cfs get myinfile:mycfsdir/myinfile
fc -02 -o mya.out mysrc.f
mya.out
cfs save myoutfile:mycfsdir/myoutfile
rm *
</PRE>

display as:

#!/bin/csh
cd $SCR
cfs get mysrc.f:mycfsdir/mysrc.f
cfs get myinfile:mycfsdir/myinfile
fc -02 -o mya.out mysrc.f
mya.out
cfs save myoutfile:mycfsdir/myoutfile
rm *

The <PRE> tag can be used with an optional WIDTH attribute that specifies the maximum number of
characters for a line. WIDTH also signals your browser to choose an appropriate font and indentation
for the text.

Hyperlinks can be used within <PRE> sections. You should avoid using other HTML tags within <PRE>
sections, however.

Note that because <, >, and & have special meanings in HTML, you must use their escape
sequences (<, >, and &, respectively) to enter these characters. See the section Escape
Sequences for more information.

Extended Quotations

Use the <BLOCKQUOTE> tag to include lengthy quotations in a separate block on the screen. Most
browsers generally change the margins for the quotation to separate it from surrounding text.

In the example:

Omit needless words.
<BLOCKQUOTE>
Vigorous writing is concise. A sentence should
contain no unnecessary words, a paragraph no unnecessary
sentences, for the same reason that a drawing should have
no unnecessary lines and a machine no unnecessary parts.

--William Strunk, Jr., 1918 
</BLOCKQUOTE>

the result is:

Omit needless words.

Vigorous writing is concise. A sentence should contain no unnecessary words, a
paragraph no unnecessary sentences, for the same reason that a drawing should
have no unnecessary lines and a machine no unnecessary parts.

--William Strunk, Jr., 1918

Forced Line Breaks/Postal Addresses

The tag forces a line break with no extra (white) space between lines. Using elements for
short lines of text such as postal addresses results in unwanted additional white space. For
example, with
:

Candycorn, Co. 
605 East Lollipop Avenue 
Candyland, TX 12345 

The output is:

Candycorn, Co.
605 East Lollipop Avenue
Candy, TX 12345

Horizontal Rules

The <HR> tag produces a horizontal line the width of the browser window. A horizontal rule is useful to
separate major sections of your document.

You can vary a rule's size (thickness) and width (the percentage of the window covered by the rule).
Experiment with the settings until you are satisfied with the presentation. For example:

<HR SIZE=4 WIDTH="50%">

displays as:

Character Formatting

HTML has two types of styles for individual words or sentences: logical and physical. Logical styles
tag text according to its meaning, while physical styles indicate the specific appearance of a section.
For example, in the preceding sentence, the words "logical styles" was tagged as "emphasis." The
same effect (formatting those words in italics) could have been achieved via a different tag that tells
your browser to "put these words in italics."

Logical Versus Physical Styles

If physical and logical styles produce the same result on the screen, why are there both?

In the ideal SGML universe, content is divorced from presentation. Thus SGML tags a level-one
heading as a level-one heading, but does not specify that the level-one heading should be, for
instance, 24-point bold Times centered. The advantage of this approach (it's similar in concept to
style sheets in many word processors) is that if you decide to change level-one headings to be
20-point left-justified Helvetica, all you have to do is change the definition of the level-one heading in
your Web browser. Indeed, many browsers today let you define how you want the various HTML tags
rendered on-screen using what are called cascading style sheets, or CSS. CSS is more advanced
than HTML, though, and will not be covered in this Primer. (You can learn more about CSS at the
World Wide Web Consortium CSS site.)

Another advantage of logical tags is that they help enforce consistency in your documents. It's easier
to tag something as <H1> than to remember that level-one headings are 24-point bold Times
centered or whatever. For example, consider the tag. Most browsers render it in bold text.
However, it is possible that a reader would prefer that these sections be displayed in red instead.
(This is possible using a local cascading style sheet on the reader's own computer.) Logical styles
offer this flexibility.

Of course, if you want something to be displayed in italics (for example) and do not want a browser's
setting to display it differently, you should use physical styles. Physical styles, therefore, offer
consistency in that something you tag a certain way will always be displayed that way for readers of
your document.

Try to be consistent about which type of style you use. If you tag with physical styles, do so throughout
a document. If you use logical styles, stick with them within a document. Keep in mind that future
releases of HTML might not support certain logical styles, which could mean that browsers will not
display your logical-style coding. (For example, the <DFN> tag -- short for "definition", and typically
displayed in italics -- is not widely supported and will be ignored if the reader's browser does not
understand it.)

Logical Styles

<DFN>
for a word being defined. Typically displayed in italics. (NCSA Mosaic is a World Wide Web
browser.)

for emphasis. Typically displayed in italics. (Consultants cannot reset your password unless
you call the help line.)
<CITE>
for titles of books, films, etc. Typically displayed in italics. (A Beginner's Guide to HTML)
<CODE>
for computer code. Displayed in a fixed-width font. (The <stdio.h> header file)
<KBD>
for user keyboard entry. Typically displayed in plain fixed-width font. (Enter passwd to change
your password.)
<SAMP>
for a sequence of literal characters. Displayed in a fixed-width font. (Segmentation fault: Core
dumped.)

for strong emphasis. Typically displayed in bold. (NOTE: Always check your links.)
<VAR>
for a variable, where you will replace the variable with specific information. Typically displayed
in italics. (rm filename deletes the file.)

Physical Styles


bold text

italic text
<TT>
typewriter text, e.g. fixed-width font.

Escape Sequences (a.k.a. Character Entities)

Character entities have two functions:

escaping special characters
displaying other characters not available in the plain ASCII character set (primarily characters
with diacritical marks)

Three ASCII characters--the left angle bracket (<), the right angle bracket (>), and the ampersand
(&)--have special meanings in HTML and therefore cannot be used "as is" in text. (The angle brackets
are used to indicate the beginning and end of HTML tags, and the ampersand is used to indicate the
beginning of an escape sequence.) Double quote marks may be used as-is but a character entity
may also be used (").

To use one of the three characters in an HTML document, you must enter its escape sequence
instead:

<
the escape sequence for <
>
the escape sequence for >
&
the escape sequence for &

Additional escape sequences support accented characters, such as:

ö
a lowercase o with an umlaut: ö
ñ
a lowercase n with a tilde: ñ
È
an uppercase E with a grave accent: È

You can substitute other letters for the o, n, and E shown above. Visit the World Wide Web
Consortium for a complete list of special characters.

NOTE: Unlike the rest of HTML, the escape sequences are case sensitive. You cannot, for instance,
use &LT; instead of <.

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