HTML Language


Ok, HTML (Hyper Text Markup Language) isn't really a programming language: it's a way to say to web browsers HOW they have to show a certain text page. By using HTML, you can say to the web browser: 'this is a title, this is just simple text, this is a link to another page, this is an image' and so on...An HTML page is usually called 'document'. All you need to build your HTML page is a simple text editor! The commands to 'talk' to a web browser are called 'TAGs'. Every tags always start with '<something> and end with </something>. As a consequence, you can't simply write '<' or '>' characters. In fact, if you write something - which isn't a tag - whithin '<' and '>' characters, say: '<this isn't a tag>', the web browser will interpret it as a tag, and that will cause an error. There is the same probem with special characters such as accented letters. So, there is a way to write these characters: &name. Where 'name' is a specific name according to ISO 8859/1 standard. For example, the '<' character's name is &lt (it means 'less than') and the '>' character's name is &gt (it means 'greater than'). This is the ISO characters set. However you could also write so: &#ASCII, where ASCII is the character as specified by ASCII code. For example, '<' is 60 and '>' is 62 (according to the ASCII code) so you could write &#60something&#62 instead of &ltsomething&gt. Each of them will be interpreted as: <something>.

HTML pages are connected each other by means of links. However you haven't to forget that you can specify links to other HTML pages, to Gopher services, to FTP hosts, to Newsgroups, to local files and so on. But now I have to explain you a bit more about these links. HTML was developed in 1989 by some CERN's researchers. First of all they defined a way to 'link' different services and documents each other. So they defined URLs. An URL (Uniform Resource Locator) is something like this: http://www.wowarea.com. But also ftp://ftp.wowarea.com is an URL. In other words, the URL's structure is: service://IP_address. Services are:

  1. http (World Wide Web)
  2. gopher (Gopherspace)
  3. telnet (Telnet session)
  4. ftp (FTP host)
  5. file (local files)
  6. tn3270 (a kind of Telnet with 3270 terminals)
  7. mailto (e-mails)
  8. news (Newsgroups)

After the name of service, there is '://' and then the IP address. After 'mailto' and 'news', there is just ':', without '//'. IP addresses are 4 series of numbers divided each other by the 'point' symbol. Like this: 123.123.123.123. So this is an URL for example: http://123.123.123.123. But you can't remember all these numbers, so each IP address has a corresponding address which is more natural for humans. Well, now you know the meaning of this link for example: ftp://ftpsite.com/pub/usr/software/file.exe... No, you can't yet. I haven't explained you that URLs are composed by: the service, the IP-address (or name), and, often the 'path' and sometimes a 'port'. What's a 'path'? Well, computers disks are often organized by using 'folders' or 'directory' or 'subdirectory'. So in that URL, the 'ftpsite' site has a 'pub' directory which contains a 'usr' directory which contains a 'software' directory which contains a file called 'file.exe'. A port is a number used to define a certain service, so, for example, FTP services usually use the '21' port and Telnet services use the '23' port.

Ok, now let's talk about HTML documents' structure...Every HTML documents have this structure:

<html>

<head>
</head>
<body>
</body>

</html>

So open your favourite text editor, then type the red text above. Finally save it as 'Mypage.html'. This is an HTML page!

Remarks start with '<!-' and end with '->', so: <!- this is a remark ->

Text within <head> and </head> tags give high level information about the document itself to the web browser. So for example you can put here the title of a page by means of <title> and </title> tags:

<html>

<head>

<title>this is this page's title!</title>

</head>
<body> Here you can write your text. This is the body of your page and you can write all you prefer within the <body> and the </body> tags...if you use remarks, web browsers will ignore them, so this text: <!- this is a remark, and browsers won't show it!-> will be hidden...
</body>

</html>

Within the 'body' tags, you can define general rules about HOW you want your page is shown. So here you have to define background's colors, text's colors and links' colors. Colors are defined by means of an 'hexadecimal notation' called RGB (Red, Green and Blue colors). You have to use this notation so: #nnnnnn, where 'nnnnnn' are hexadecimal numbers. For example '#000000' means 'black' and '#ffffff' means 'white'. Don't worry: there is a table containing colors and corresponding hexadecimal notation here! So this is the <body> tag's structure:

<body bgcolor="#nnnnnn" text="#nnnnnn" link="#nnnnnn" vlink="#nnnnnn" alink="#nnnnnn"></body>

  1. Bgcolor defines your page's background color.
  2. text define your page's text color.
  3. link define your page's links color.
  4. vlink define your page's visited links color (vlink means 'Visited LINK).
  5. alink define your page's active links color (alink means 'Active LINK'). So, if you define your color alinks, say red, when you click on any link it change its color to red.

Just another thing: you can put an image inside of background parameter. For example you can write so: background="image.gif" instead of an hexadecimal number. So you will see your image shown on all the page! Ok, now you can write your FIRST (rough) web page!

However there are several tags which you should know:

And finally another last thing: each web browser is different from all others. So the same page will be a bit different according to the used web browser: Netscape or Internet Explorer...


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