. You don`t have to use capital letters within tags, but it does help to make them stand out within the text of your document when you come back later on to revise it.
These tags can perform several functions:
- Identify the structure of the document (e.g., section headers, blocks of text such as extended quotes, bulleted lists).
- Provide explicit instructions to the browser as to how to display specific portions (e.g., boldface, italics, fixed-pitch font).
- Tell the browser where to display embedded graphic images.
- Create links within and between documents.
Whenever your web browser asks a web server for a document, the server
sends the browser a copy of the HTML source for the requested web page.
The browser, in turn, parses the source and displays the formatted page
on your screen. (You can choose "Page Source" (Netscape) or "Source" (Explorer) from the "View" menu and take a look at the
HTML source for any page). It is the browser that interprets and knows
the meaning of the tags in an HTML source file.
HTML markup tags come in two flavors, free-standing and paired:
- Free-standing tags typically either cause an immediate effect, or apply until a contrary tag is found.
Here is an example of a free-standing tag in HTML:
This tag causes the browser to move to a new line, draw a horizontal rule (a straight line between the margins, such as immediately follows this sentence), and move to the following line.
We will discuss horizontal rules in more detail later in this class and again in HTML II.
- Paired tags enclose a block of text to which they apply. The two tags of a pair have the same keyword, but the closing tag starts with a slash character. This will become clearer as we work our way through an example of a paired markup tag in HTML:
Until you become familiar with the syntax of HTML markup, it can be a little confusing
to encounter tags in the middle of a paragraph and figure out what they mean. Let`s
"dissect" these tags, taking a look at each part ("token" in the jargon).
The browser first "reads in" the token "<". At
that point, the browser knows that the text following the "<" symbol
is a markup tag. It then reads more characters until it finds a ">"
symbol. Then, the browser attempts to decipher the material between those angle brackets, interpreting it as a tag. If it can find that tag in its programmed-in list of rules, it
formats the text that follows it accordingly. If it cannot find that tag on its list, it ignores it. So, any text that
follows a markup tag is formatted on your screen according to the
rules for that tag that are programmed into the browser, if any.
How do we turn off a tag once it has been read
and interpreted by a browser?
Paired tags have a start tag and an end tag. Start tags are
the tag name surrounded by "<" and ">". End tags have the same
name as their start tag counterpart, but have a "/" after the "<", before the name of
the tag. If you look at our example, it will become more clear:
Notice that after the word Greetings! there is another tag, but this
time the tag is slightly different, in that there is a "/" in front of
the tag name. Think of the end tag as the "off" switch. By putting
in an end tag, you are telling the browser that you no longer want the
text formatted according to the rules for that tag.
Let`s see an example in action:
- The HTML:
This is some text followed by some more text that I don`t want to blink.
- The above will look like the following when parsed and displayed by the web browser:
This is some text followed by some more text that I don`t want to blink.
Your web browser reads in the tag and stops the formatting, in this case
turning BLINK off.
So now you have learned two things:
- How a web browser formats web pages based on markup, and
- How annoying the BLINK tag is.
Language
in our case is regarded as the set of tags that a web browser
can understand, and the rules it will follow in displaying the tagged text.
HTML is an example of the distinction between "de jure" and "de facto" standards. Only a few versions of HTML have gone through the official international standardization process. The technology of HTML is still changing so rapidly that there are many different versions of HTML in use. (The previous sentence was included in the 1994 version of this page, and remains true!) Each browser defines an HTML "standard" according to what tags it will recognize and how it will format the tagged text for display. When the authors of other browsers decide that somebody else`s new tag is a good idea and include it in the next version of their browser, it gradually becomes "standard."
As an author of web pages, it is your responsibility to decide which tags to use, knowing that using a tag that will be ignored by some browsers means that your page will not look the way you want it to when viewed by people using those browsers.
