Is it hard to Learn?

How Peopl does Access the Web?

• through using
• Browsers
• Web Servers
• Screen readers
• Devices

How the Web Works?

• When you visit a website, the web server hosting that site could be anywhere in the world. In order for you to find the location of the web server, your browser will first connect to a Domain Name System (DNS) server.

• Your computer contacts a network of servers called Domain Name System (DNS) servers. These act like phone books; they tell your computer the IP address associated with the requested domain name. An IP address is a number of up to 12 digits separated by periods / full stops. Every device connected to the web has a unique IP address; it is like the phone number for that computer.

• The unique number that the DNS server returns to your computer allows your browser to contact the web server that hosts the website you requested. A web server is a computer that is constantly connected to the web, and is set up especially to send web pages to users.

• The web server then sends the page you requested back to your web browser.

HTM L Us es El ements to Describe theStructure of Pages

• Tags act like containers. They tell you something about the information that lies between their opening and closing tags.

Attributes Tell Us More About El ements

• Attributes provide additional information about the contents of an element. They appear on the opening tag of the element and are made up of two parts: a name and a value, separated by an equals sign.

• HTML5 allows you to use uppercase attribute names and omit the quotemarks, but this is not recommended.

The majority of attributes can only be used on certain elements, although a few attributes (such as lang) can appear on any element.

Most attribute values are either pre-defined or follow a stipulated format. We will look at the permitted values as we

introduce each new attribute. The value of the lang attribute is an abbreviated way of specifying which language is used inside the element that all browsers understand.

Escape Characters

• There are some characters that are used in and reserved by HTML code. (For example, the left and right angled brackets.)

Therefore, if you want these characters to appear on your page you need to use what are termed “escape” characters (also known as escape codes or entity references). For example, to write a left angled bracket, you can use either < or <. For an ampersand, you can use either & or &. There are also special codes that can be used to show symbols such as copyright and trademark, currency symbols, mathematical characters, and some punctuation marks. For example, if you want to include a copyright symbol on a web page you can use either © or ©. When using escape characters, it is important to check the page in your browser to ensure that the correct symbol shows up. This is because some fonts do not support all of these characters and you might therefore need to specify a different font for these characters in your CSS code.

Site Maps

• The aim is to create a diagram of the pages that will be used to structure the site. This is known as a site map and it will show how those pages can be grouped. To help you decide what information should go on each page, you can use a technique called card sorting. This involves placing each piece of information that a visitor might need to know on a separate piece of paper and then organizing the related information into groups. Each group relates to a page and, on larger sites the, pages can in turn can be grouped together to create different sections of the website. The groups of information are then turned into the diagram that is known as the site map. Sometimes it can be helpful to ask people who are the target audience to help you group related information together. A site map will usually begin with the homepage. Additionally, if the site is large and is compartmentalized into sections, each section might require its own section homepage to link to all of the information within it. For example, most online shops have section homepages for each type of product, which then in turn link to individual product pages. You may need to duplicate some information if it needs to appear on more than one page. The pages (or groups of pages) will inform how users navigate through the site. Remember to focus on the goals that your visitors want to achieve. It is worth noting that the site owner might organize information in a way that is different to what the public expects. It is important to reflect the public’s understanding of the subject (rather than just the site owner’s understanding of it).

HOW A BROWSER SEES A WEB PAGE

• In order to understand how you can change the content of an HTML page using JavaScript, you need to know how a browser interprets the HTML code and applies styling to it.

1. RECEIVE A PAGE AS HTML CODE
2. CREATE A MODEL OF THE PAGE AND STORE IT IN MEMORY
3. USE A RENDERING ENGINE TO SHOW THE PAGE ON SCREEN

• All major browsers use a JavaScript interpreter to translate your instructions (in JavaScript) into instructions the computer can follow.

When you use JavaScript in the browser, there is a part of the browser that is called an interpreter (or scripting engine). 40 THE ABC OF PROGRAMMING The interpreter takes your instructions (in JavaScript) and translates them into instructions the browser can use to achieve the tasks you want it to perform. In an interpreted programming language, like JavaScript. each line of code is translated one-by-one as the script is run.