An interactive introduction to HTML and CGI scripts on the WWW (courseware)

Basic HTML formatting tags

Introduction to HTML

Simple formatting tags

Logical formatting tags

Paragraph and line breaks

Headings and rulers

Insertion of in-line images

A background image

Creating a list of items

Hyper text links

URL

Tables

Single cell

Row(s) of cells

Heading to a column

Spanning rows and columns

Using HTML Special characters

Literal copy and centering of text

Inserting an e-mail address

Warning if you are not using a browser that supports tables
such as Netscape 1.1 or later then this page
will probably be very difficult to read.

Introduction to HTML

HTML (HyperText Markup Language) is a markup language which consists of tags embedded in the text of a document. The browser reading the document interprets these markup tags to help format the document for subsequent display to a reader. However, many of the decisions about layout are made by the browser. Remember, web browsers are available for a wide variety of computer systems.

The browser thus displays the document with regard to features that the viewer selects either explicitly or implicitly. Factors affecting the layout and presentation include:

The markup tags used.
The physical page width.
The fonts used to display the text.
The colour depth of the display.

The browser, ignores extra spaces and new lines between words and markup tags when reading the document. Thus, the following three text fragments will be formatted identically.

Fragment 1 Fragment 2 Fragment 3
The browser will ignore
new lines and extra
spaces in the text. The browser will
ignore new lines and
extra spaces in the text. The browser will
ignore new lines and
extra spaces in the text.

Fragment 1	Fragment 2	Fragment 3
The browser will ignore new lines and extra spaces in the text.	The browser will ignore new lines and extra spaces in the text.	The browser will ignore new lines and extra spaces in the text.

to produce the following:

The browser will ignore new lines and extra spaces in the text.

The markup language is made up of tags such as <B> which requests text that follows to be in bold type. This bolding is turned off by the inverse markup tag </B>.

In writing a tag, the case of the letters in the tag name is unimportant so that <B> and <b> represent the same tag.

The basic layout of an HTML document and the resultant information displayed by a browser such as netscape is shown below:

Displayed by browser HTML markup required

An example of a simple web page.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> <HTML> <HEAD> <TITLE>Title of the web page </TITLE> </HEAD> <BODY> An example of a simple <B>web</B> page. </BODY> </HTML>

Displayed by browser	HTML markup required
An example of a simple web page.	<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> <HTML> <HEAD> <TITLE>Title of the web page </TITLE> </HEAD> <BODY> An example of a simple <B>web</B> page. </BODY> </HTML>

The tags used are:

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML //EN">: Informs the browser that this is an HTML document. This is an SGML tag to identify the version of HTML being used, in this case just HTML. Version 3 browsers (e.g. Netscape) are happy about this pretense that this document is just plain HTML.
<HTML> </HTML>: Defines the extent of the HTML markup text
<HEAD> </HEAD>: Contains descriptions of the HTML page. This meta information is not displayed as part of the web page.
<TITLE> </TITLE>: Describes the title of the page. This description is usually displayed by the browser as the title of the window in which the web page is displayed. This information is also used by some search engines to compile an index of web pages.
<BODY> </BODY>: Delimits the body of the web page. In the body is the text to be displayed as well as HTML markup tags to hint at the format of the text.
<B> </B>: Displays the enclosed text in a bold typeface.

Note:: The tags can be written in upper-case or a mixture of upper- and lower-case or just lower-case. For example, <HTML>, <HtMl> and <html> all represent the same tag.

Simple formatting tags

The following are some of the simple formatting tags available in HTML.

Formatted text HTML markup required

The text is bolded.
The <B>text</B> is bolded.

The text is italicized.
The <I>text</I> is italicized.

The text is in a teletype font.
The <TT>text</TT> is in a teletype font.

The text is 2 sizes larger. The size attribute may also be an absolute value in the range 1 .. 7.
The <FONT SIZE=+2>text</FONT> is 2 sizes larger. The size attribute may also be an absolute value in the range 1 .. 7.

Use the e-mail address
M.A.Smith@brighton.ac.uk
to contact me.
Use the e-mail address <ADDRESS>M.A.Smith@brighton.ac.uk</ADDRESS> to contact me.

Formatted text	HTML markup required
The text is bolded.	The <B>text</B> is bolded.
The text is italicized.	The <I>text</I> is italicized.
The `text` is in a teletype font.	The <TT>text</TT> is in a teletype font.
The text is 2 sizes larger. The size attribute may also be an absolute value in the range 1 .. 7.	The <FONT SIZE=+2>text</FONT> is 2 sizes larger. The size attribute may also be an absolute value in the range 1 .. 7.
Use the e-mail address M.A.Smith@brighton.ac.uk to contact me.	Use the e-mail address <ADDRESS>M.A.Smith@brighton.ac.uk</ADDRESS> to contact me.

Note:: How the formatting is turned off by the inverse of the HTML formatting tag.

Logical formatting tags

The following are some of the logical formatting tags in HTML. These should be used to describe a logical unit of your document. The formatting of this logical unit may in some cases be the same as produced by other formatting tags. Remember, the tags specify logical units of the document, software other than the web browser may need this information.

Formatted text HTML markup required

The following is a citation.
The following is
<CITE>a citation.</CITE>

Represents computer code
<CODE> Represents computer code </CODE>

A sequence of literal characters
A sequence of <SAMP>literal characters</SAMP>

Note:
This is a blockquote of some text

Note:<BLOCKQUOTE>This is a blockquote of some text </BLOCKQUOTE>

The following is a definition
The following is
<DFN>a definition</DFN>

The following text is emphasized.
The following <EM>text</EM>
is emphasized.

keyboard characters.
<KBD>keyboard characters</KBD>

The following text is strongly emphasized
The following <STRONG>text</STRONG>
is strongly emphasized

The following name is a program variable
The following <VAR>name</VAR>
is a program variable

Formatted text	HTML markup required
The following is a citation.	The following is <CITE>a citation.</CITE>
`Represents computer code`	<CODE> Represents computer code </CODE>
A sequence of `literal characters`	A sequence of <SAMP>literal characters</SAMP>
Note: This is a blockquote of some text	Note:<BLOCKQUOTE>This is a blockquote of some text </BLOCKQUOTE>
The following is a definition	The following is <DFN>a definition</DFN>
The following text is emphasized.	The following <EM>text</EM> is emphasized.
`keyboard characters`.	<KBD>keyboard characters</KBD>
The following text is strongly emphasized	The following <STRONG>text</STRONG> is strongly emphasized
The following `name` is a program variable	The following <VAR>name</VAR> is a program variable

Paragraph and line break

A new paragraph is started with the <P> tag, and may be optionally terminated with the inverse paragraph tag </P>. However, it is usual not to specify the inverse paragraph tag </P>

A line break is created by the <BR> tag, which has no inverse tag.

Formatted text HTML markup required

Last sentence of a paragraph
The first line of a new paragraph.

Last sentence of a paragraph <P> The first line of a new paragraph.

A line of text.
On a new line.
A line of text. <BR> On a new line.

Formatted text	HTML markup required
Last sentence of a paragraph The first line of a new paragraph.	Last sentence of a paragraph <P> The first line of a new paragraph.
A line of text. On a new line.	A line of text. <BR> On a new line.

Headings and rulers

A heading in the text is created with the <H1> tag. There are in fact six heading tags <H1> the largest to <H6> the smallest.

Formatted text HTML markup required

An H1 heading

<H1>An H1 heading</H1>

An H3 heading

<H3>An H3 heading</H3>

An H6 heading

<H6>An H6 heading</H6>

Formatted text	HTML markup required
An H1 heading	<H1>An H1 heading</H1>
An H3 heading	<H3>An H3 heading</H3>
An H6 heading	<H6>An H6 heading</H6>

A heading tag generates line break(s) before and after the heading text. For example:

Formatted text HTML markup required

Just before the heading.
An H4 heading
Just after the heading.
Just before the heading. <H4>An H4 heading</H4> Just after the heading.

Formatted text	HTML markup required
Just before the heading. An H4 heading Just after the heading.	Just before the heading. <H4>An H4 heading</H4> Just after the heading.

A horizontal ruler across the page can be created with the <HR> tag. For example:

Formatted text HTML markup required

End of a section
New section
End of a section<HR>New section

Only 40% of width
New section
Only 40% of width<HR WIDTH=40%>New section

The size of the ruler
New section
The size of the ruler<HR SIZE=10>New section

Formatted text	HTML markup required
End of a section New section	End of a section<HR>New section
Only 40% of width New section	Only 40% of width<HR WIDTH=40%>New section
The size of the ruler New section	The size of the ruler<HR SIZE=10>New section

Note:

The size of the ruler is by default specified in pixels.

Insertion of in-line images

As well as text, images may be inserted into the document. An image may be held in several formats, though the main ones used are GIF and JPEG. Due to limited bandwidth, JPEG with its high compression of picture data and its ability to represent 24 bit colour images is the best to use. Even though the JPEG compression is lossy the degradation of picture quality is not very noticeable to the human eye.

However, if the picture is very small or a graphical image then the GIF format may be the best.

Inserted image HTML markup required

mas jpeg
<IMG SRC="mas_fn50.jpg" ALT="mas" ALIGN=TOP>jpeg

A gif image with a transparent background.
A gif image <IMG SRC="sdot.gif" ALIGN=TOP> with a transparent background

mas Text can be made to flow around an image on the left hand side by using the attribute ALIGN=RIGHT.
<IMG SRC="mas_fn50.jpg" ALT="mas" ALIGN=RIGHT> Text can be made to flow around an image on the left hand side by using the attribute ALIGN=RIGHT.

Inserted image	HTML markup required
jpeg	<IMG SRC="mas_fn50.jpg" ALT="mas" ALIGN=TOP>jpeg
A gif image with a transparent background.	A gif image <IMG SRC="sdot.gif" ALIGN=TOP> with a transparent background
Text can be made to flow around an image on the left hand side by using the attribute ALIGN=RIGHT.	<IMG SRC="mas_fn50.jpg" ALT="mas" ALIGN=RIGHT> Text can be made to flow around an image on the left hand side by using the attribute ALIGN=RIGHT.

Note:: There are many graphic editing programs which allow you to specify that one of the colours of a gif image is transparent when displayed by a browser. For example, LView Pro 1.B2 and Paint Shop Pro 3.11, allow the creation of a transparent colour in a gif image. However, in order to do this, the version used for the saved gif image must be 89a.
An image may be used as the displayed item for a hypertext link. For example: <A HREF="..."> <IMG SRC="..."> </A>.

The attributes of the <IMG> tag include:

ALT="mas": Causes mas to be displayed instead of the image. This will occur if the browser can not display images or the display of images has been suppressed.
ALIGN=TOP: Causes any following text to be displayed aligned with the top of the picture.
ALIGN=BOTTOM.: Causes any following text to be displayed aligned with the bottom of the picture.
ALIGN=MIDDLE.: Causes any following text to be displayed aligned with the middle of the picture.
ALIGN=LEFT: Cause the image to be left aligned on the page. Text is flowed around the image on the right hand side.
ALIGN=RIGHT: Cause the image to be right aligned on the page. Text is flowed around the image on the left hand side.

Insertion of a background image

The document may be given a background image. The selected image is tiled across the document and then the text of the document is written over the image(s). It is thus important to choose a background image that will not be too distracting for the reader. The background image is achieved by adding a background attribute to the BODY markup tag. For example:

Creating a list of items

There are several types of list, an un-ordered list can be created by the following markup:

Formatted text HTML markup required

Item one of list
Item two of list

<UL> <LI>Item one of list <LI>Item two of list </UL>

Formatted text	HTML markup required
Item one of list Item two of list	<UL> <LI>Item one of list <LI>Item two of list </UL>

An ordered list is similar to an un-ordered list, except that each entry is consecutively numbered.

Formatted text HTML markup required

Item one of list
Item two of list

<OL> <LI>Item one of list <LI>Item two of list </OL>

Formatted text	HTML markup required
Item one of list Item two of list	<OL> <LI>Item one of list <LI>Item two of list </OL>

A definition list allows a list with a backward hanging indent to be created.

Formatted text HTML markup required

Definition tag.
Text of the definition list. Which may stretch over several lines.
Another definition tag.
Text of the definition list.

<DL> <DT> Definition tag. <DD> Text of the definition list. Which may stretch over several lines. <DT> Another definition tag. <DD> Text of the definition list. </DL>

Formatted text	HTML markup required
Definition tag. Text of the definition list. Which may stretch over several lines. Another definition tag. Text of the definition list.	<DL> <DT> Definition tag. <DD> Text of the definition list. Which may stretch over several lines. <DT> Another definition tag. <DD> Text of the definition list. </DL>

Note:: It is a common practice for the definition tag with an image or even have it prefixed with an image.

Hyper text links

A hyper text link allows a browser of the document to navigate either: to a new point in the document or to navigate to a different document. A named point in a document is specified with an anchor tag which has the attribute NAME. For example:

Formatted text HTML markup required

Here <A NAME="marker"> Here </A>

Formatted text	HTML markup required
Here	<A NAME="marker"> Here </A>

Note:: There does not need to be any text to visibly name the anchor point.

To effect a transfer to a named anchor point, the HREF form of the anchor tag is used. For example:

Formatted text HTML markup required

Transfer to anchor <A HREF="#marker"> Transfer to anchor </A>

Formatted text	HTML markup required
Transfer to anchor	<A HREF="#marker"> Transfer to anchor </A>

The # before the name of the hypertext link tells the browser that the link is to a named point in a document. As no document name is specified before the # the hypertext link is to a point in the current document. It is usual for the browser to visibly highlight the hypertext link.

Hypertext links may also link to other documents, in which case the HREF component names the document. If the file is held on another machine then a URL (Uniform Resource Locator) is used to describe the location of the document. For example:

Hyper text link to the file
file.htm Hyper text link to the file
file.htm held on another machine using an URL
<A HREF="file.htm"> Name </A> <A HREF="http://host/file.htm"> Name </A>

To go to a named point in a file the format of the anchor is:

Hyper text link to the file
file.htm at point mark Hyper text link to the file
file.htm at point mark held on another machine using an URL
<A HREF="file.htm#mark"> Name </A> <A HREF="http://host/file.htm#mark"> Name </A>

URL (Uniform Resource Locator)

The URL is used to specify the location of a file held on a remote machine. This is composed of several distinct components. For example, the URL http://host/file.htm is composed of the following components.

http: The protocol that is to be used to access the file. In this case the HyperText Transfer Protocol. There are other protocols, but they are used infrequently.
host: The name of the machine, this can be either a symbol name such as snowwhite.it.brighton.ac.uk or a numeric IP (Internet Protocol) address such as 193.200.1.1.
file.htm: The path name of the file to which the hypertext link is to be made. This is relative to the base directory in which web pages are held. The location of this directory htdocs is defined by the person who has set up the web server.
Unix based web servers allow a convenient shortcut to accessing files placed in the directory public_html in the user's home directory. For example, the file home.htm placed in the directory public_html in mas's home directory on the server machine snowwhite.it.brighton.ac.uk, can be accessed with the URL http://snowwhite.it.brighton.ac.uk/~mas/home.htm

In creating the URL the characters space, =, +, <, >, %, ", /, and ? should not be used. If you do need to include these characters then represent them by the % symbol followed by the hexadecimal value of the character. The space character however, can also be represented by the character +. For example, http://snowwhite.it.brighton.ac.uk/%25.htm represents the URL http://snowwhite.it.brighton.ac.uk/%.htm.

Other access protocols can be specified by an URL. For example, to access files via the FTP (File Transfer Protocol) an URL of the form:

ftp://ftp.brighton.ac.uk/pub/mas/ada95

is used. This specifies that a link to the file/directory mas/ada95 on the machine ftp.brighton.ac.uk should be made. If mas/ada95 is a directory the viewer is presented with a list of files in the directory, otherwise the file will be displayed/transferred to you.

The full specification for an URL is:

Protocol Format Notes
HTTP http://host[:port]/path -
FTP ftp://[username[:password]@host/path If no username is specified the user anonymous is used.
Gopher gopher://host[:port]/[type[item]] -

Protocol	Format	Notes
HTTP	http://host[:port]/path	-
FTP	ftp://[username[:password]@host/path	If no username is specified the user anonymous is used.
Gopher	gopher://host[:port]/[type[item]]	-

Note:: In describing the format of an URL items enclosed in [ ]'s are optional.

Tables

Single cell

A table is created using the <TABLE> markup tag. The simplest table consists of a single data cell. The markup <TD> defines the start of a table data cell. Netscape requires a termination tag </TD>.

The status of the tag </TD> is somewhat unclear. Netscape 1.1 requires the end of table data cell tag </TD> to terminate the cell in certain circumstances. Other browsers sense the end of the cell by the </TABLE> or other formatting tag. The tag </TD> is not defined in the HTML specification. As unrecognized tags are ignored by a browser putting the tag in does no harm.

Formatted text HTML markup required

Text in a table

<TABLE BORDER CELLPADDING=2> <TD> Text in a table </TD> </TABLE>

The following extra components can be added to a table tag:

UNITS=: Either en, relative or pixels. This defines the units that will be used in defining other attributes. The default is pixels.
BORDER: Specifies that a border is to be placed around the table cells. The width of the border is optionally specified with BORDER=n.
CELLPADDING: Specifies the gap to be placed around the table contents.

If the text in the data cell is to be left aligned the additional component ALIGN=LEFT can be added to the <TD> tag. For example:

<TD ALIGN=LEFT>

Other alignments are ALIGN=RIGHT, ALIGN=CENTER.

Row(s) of cells

A row of cells can be created by repeating the <TD> tag.

Formatted text HTML markup required

Data cell 1 Data cell 2

<TABLE BORDER CELLPADDING=2> <TD> Data cell 1 </TD> <TD> Data cell 2 </TD> </TABLE>

To form a table of many rows, the markup tag <TR> is inserted where each new row in the table starts.

Formatted text HTML markup required

Data cell 1 Data cell 2
Data cell 3 Data cell 4

<TABLE BORDER CELLPADDING=2> <TD> Data cell 1 </TD> <TD> Data cell 2 </TD> <TR> <TD> Data cell 3 </TD> <TD> Data cell 4 </TD> </TABLE>

Heading to a column

The tag <TH> may be used instead of <TD> if the cell is a header to a column of cells. For example:

Formatted text HTML markup required

Mnemonic Expansion
HTML Hyper Text
Markup Language

<TABLE BORDER CELLPADDING=2> <TH ALIGN=LEFT> Mnemonic</TH> <TH ALIGN=LEFT> Expansion </TH> <TR> <TD> HTML</TD> <TD> Hyper Text<BR>Markup Language</TD> </TABLE>

Spanning rows and columns

The elements ROWSPAN and COLSPAN of the HTML tags <TD> and <TH> are used to form data cells which span more than one row or column. For example:

Formatted text HTML markup required

Language Encapsulation

Ada 95 Using Class
C++ Package

<TABLE BORDER CELLPADDING=2> <TH ALIGN=LEFT>Language</TH> <TH ALIGN=LEFT COLSPAN=2>Encapsulation</TH> <TR> <TD> Ada 95</TD> <TD ROWSPAN=2>Using</TD> <TD> Class</TD> <TR> <TD> C++</TD> <TD> Package</TD> </TABLE>

Using HTML special characters

The markup language uses the character < to start a markup tag. The consequence of this is that < can not be used to represent the less than character directly in a web page. The HTML markup languages defines an escape sequences of characters to represent such special characters.

The following are some of the character sequences used to represent characters that have a special meaning in the HTML language.

Character Represent by sequence Character Represent by sequence
< < > >
& & " "

Character	Represent by sequence	Character	Represent by sequence
<	<	>	>
&	&	"	"

Thus to include <BODY> as part of the text of a document the sequence <BODY> can be written.

Characters not in the normal ASCII character set are also represented by an escape sequence. This is so that they may be typed on computer systems which do not directly support the input of such characters. For example:

Character Represent by sequence Character Represent by sequence
à à ç ç

Character	Represent by sequence	Character	Represent by sequence
à	à	ç	ç

To prevent the web browser breaking a line at a space character a non breaking space character is used rather than the normal space character.. A non breaking space character is represented by the escape sequence  . This can also be used to introduce more than one space character between words. For example:

HTML Formatted text
A  B<BR>A B A B
A B

HTML	Formatted text
A  B<BR>A B	A B A B

In addition a character from the LATIN-1 character set is represented by &#nn;. Where nn represents the character code in decimal. For example:

Character Represent by sequence Character Represent by sequence
†  A A

Character	Represent by sequence	Character	Represent by sequence
†		A	A

Printable Latin-1 characters

Literal copy and centering of text

Text can be copied literally by using the <PRE> tag. However, any HTML tags in the text will be processed. For example:

Formatted text HTML markup required

* *** *****

<PRE> * *<B>*</B>* ***** </PRE>

Formatted text	HTML markup required
* * ***	<PRE> * <B></B>* ***** </PRE>

Note:: The copied text is formatted using a non proportional font to preserve the layout.

Any text to be centered is enclosed between the tags <CENTER> and </CENTER>.

Formatted text HTML markup required

A line of normally formatted text. Some lines of text
that are centered
A line of normally formatted text. <CENTER> Some lines of text <BR> that are centered </CENTER>

Formatted text	HTML markup required
A line of normally formatted text. Some lines of text that are centered	A line of normally formatted text. <CENTER> Some lines of text <BR> that are centered </CENTER>

Inserting an e-mail address

An e-mail address may be inserted into the document using a special form of the anchor markup tag. A user selecting this will be presented with a form on which to prepare their message for eventual sending in this case to the e-mail address:

M.A.Smith@brighton.ac.uk

Formatted text HTML markup required

Mail me
<A HREF="mailto:M.A.Smith@brighton.ac.uk">Mail me</A>

Formatted text	HTML markup required
Mail me	<A HREF="mailto:M.A.Smith@brighton.ac.uk">Mail me</A>

Of course your browser has to support this facility.

Warning if you are not using a browser that supports tables
such as Netscape 1.1 or later then this page
will probably be very difficult to read.

To my global Home page Comments, suggestions etc. to:
M.A.Smith@brighton.ac.uk
CGI List of: CGI Environment variables

Hyper text link to the file `file.htm`	Hyper text link to the file `file.htm` held on another machine using an URL
<A HREF="file.htm"> Name </A>	<A HREF="http://host/file.htm"> Name </A>

Hyper text link to the file `file.htm` at point `mark`	Hyper text link to the file `file.htm` at point `mark` held on another machine using an URL
<A HREF="file.htm#mark"> Name </A>	<A HREF="http://host/file.htm#mark"> Name </A>

Basic HTML formatting tags

Contents

Introduction to HTML

Simple formatting tags

Logical formatting tags

Paragraph and line break

Headings and rulers

An H1 heading

An H3 heading

An H6 heading

An H4 heading

Insertion of in-line images

Insertion of a background image

Creating a list of items

Hyper text links

URL (Uniform Resource Locator)

Tables

Single cell

Row(s) of cells

Heading to a column

Spanning rows and columns

Using HTML special characters

Literal copy and centering of text

Inserting an e-mail address