Thursday, March 31, 2016

HTML intro

Part 1 - What is HTML

Introduction

The short answer is HyperText Markup Language. 

This is a practical guide not a history lesson so I'll keep the history short. If you want to read more of how HTML developed have a look here HTML history. Early on it was decided that the internet standards would be 'open' meaning that they would published so anyone can use them. In most cases this works really well and an HTML page looks the same in Google Chrome, Mozilla Firefox and Microsoft internet explorer 9 times out of 10.

Structure

The top level is the site. A site is a collection of pages in a domain.

I think sites and pages are familiar enough but it's worth looking at what a domain is more closely. The internet is big. And every page has to have a totally unique name. Let's have a look at the unique name of a page:

http://www.ajscrafts.co.uk/common/home.aspx

And let's pick it to peices:

http://www.ajscrafts.co.uk/common/home.aspx

This is the protocol. You'll be familiar with http and https (hypertext transfer protocol(secure)) because this protocol delivers almost all web pages. We'll mainly be using http. The s is important though. If the site you are on uses https, you can be pretty sure the server you are talking to is who it says it is and that anything you send and receive is encrypted.

http://www.ajscrafts.co.uk/common/home.aspx

This is the fully qualified domain name. If you want to use a domain name you have to register it. This allows the domain name authorities to ensure domains are unique. It tells the traffic routing software exactly which server the page is held on. The servers are actually numbered, this is called the IP address. The number that relates to ajscrafts.co.uk is 91.102.64.149 right now. The number could change because the hosting shares IP addresses. Every device on the internet has it's own IP address and we are running out. A new standard is being rolled out called IPv6 but this is well beyond the discussion here.

http://www.ajscrafts.co.uk/common/home.aspx

The last part tells the server where to find the page to deliver. For convenience files can be organised into directories. The home.aspx file is in the directory common.

Pages

The important thing to us is the page. A page is a single file on a disk somewhere that can be delivered by giving its url. So let's make a page...

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