Of Servers and Clients

Before I delve into more HTML tags - as promised in my last blog - today I would like to have a look at some of the actual pieces of hardware that make the internet possible. What precisely is a web page? What is it that you see on your computer screen when you call up a page, and how does it get there?

At the most basic level, a web page is a HTML file which is being opened in a computer program which has been specifically developed for this purpose: your browser. Whether you use Firefox or Internet Explorer, Safari or Opera, or even an outdated browser like Netscape, they all do the same thing: They find the location of the file you are looking for, and render it out for you the way the web designer has envisioned it (well - at least, most of the time).

What makes a web page a bit different from your usual word document, or spreadsheet, or the holiday shots you downloaded from your photo camera, is that the file is usually not sitting on your own computer. It lives on some computer which may be in the next town, or on the other side of the country, or halfway around the globe. Apart from slight differences in loading speed, you'd never notice the difference.

The computer where the file is stored is called a *server*. You can host your website on your own computer if you have the appropriate computer equipment and software - which can be downloaded for free from the internet, and Macs even come with all the necessary software already installed. One of the disadvantages of doing this is that the computer needs to be connected to the internet 24/7, or else the website will not be available when the computer is not online. There are also security risks, such as that your site might get hacked. For this reason, most websites are hosted by a dedicated web hosting service - for a reasonably small annual fee, you can hire a certain amount of storage space for your website files, and the company provides all the necessary setup, software and security. Usually they also include a regular backup service, which can come in handy for those times when things just go wrong.

How does your browser find the right file, among all the gazillion files that make up today's internet? That is what the URL is for - that little line of text that appears in your browser navigation bar, and starts like this: http:// . "URL" stands for Uniform Resource Locator - a unique tag that tells the browser where the page (the "resource") is located. URL's don't only apply to the main HTML document that is your web page: Each and every file that makes up the page you end up seeing on your screen, has their own unique URL. For instance, if a web page displays an image, that image will be a separate file with its own unique web address, or URL. The file does not even need to be located on the same computer as the main HTML document - a page can display images, or movie, audio or flash files, which are each located on a different computer, in completely different parts of the world.

The browser's job is to locate all these files, pull them down the wires that connect the server with your own computer, and assemble them in such a way that they look nice, and make sense. Not a small job! Your own computer, when it displays a web page, is called a "client" - as opposed to server. In one of my next blogs, I will go into the difference between server-side and client-side web programming, but for now, I will call it a blog post! Otherwise, it might end up being information overload.

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