Introduction to HTML
By Stephen Bucaro
We are all familiar with the Web, many of us are a bit too familiar with the Web.
Web is a short way of saying "World Wide Web", sometimes called the "internet".
The Web consists of billions of clients (smartphones, tablet computers, laptop
computers, desktop computers, and so on) and servers (computers loaded with special
software) connected through wired and wireless networks.
A web client uses a program called a web "browser" to send a request over the internet
to a Web server. The server receives the request, finds the resource requested, and
sends it over the internet to the client's web browser.
The server usually sends the response to the browser with a set of instructions written
in HTML (HyperText Markup Language). HTML consists of tags that define the structure
of a web page. It is the standard markup language for documents to be displayed in a
web browser. All web browsers know how to display HTML page on the client device.
HTML works with technologies such as Cascading Style Sheets (CSS) and scripting languages
Then, after you have completed this book, you can move on to one that discusses those
HTML elements are the building blocks of a Web page. HTML elements are defined by tags.
A tag is an abbreviation or word written in English. Every tag is delineated using angle
brackets. A less-than character < indicates the start of a tag, this is immediately
followed by the instruction. A greater-than character > indicates the end of a tag.
An example of an instruction is <br>, which creates a line-break.
HTML provides tags to create elements such as headings <h1>, paragraphs <p>,
lists <ol>, and other items. Browsers do not display the HTML tags, but use them to
format the content of the Web page.
XML (eXtensible Markup Language) was initially defined in 1998. XML is used for storing
and transporting data. Similar to HTML, it uses tags delineated using angle brackets.
Unlike HTML, XML has strict rules about tags and their arrangement. The main rules are
XML tags are case-sensitive, all XML elements must have a closing tag, all XML elements
must be properly nested.
Because of the strict structure of XML, a version called XHTML (eXtensible HyperText Markup
Language) was specified in 2000 to replace HTML. So now, the tags used to layout web
pages must conform to the rules of XML. That means all elements must have an opening
and closing tag and the opening and closing tag instruction must be in the same case.
HTML: <p>This is my paragraph text. <p>This is a second paragraph text.
XHTML: <p>This is my paragraph text.</p> <p>This is a second paragraph text.</p>
An opening tag precedes the contents of the element. A closing tag follows the contents
of the element. A closing tag is a repeat of the opening tag, except it uses </ to
indicate the start of the tag.
Some elements, for example br (line-break) don't have any contents, so they may use
a self closing tag, for example <br/>.
In this book, I will use only code that conforms to the XHTML standard.