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Web Design Fundamentals is a survey of Web design and development techniques and technologies, fundamental concepts, terms, and best practices involved in professional web design. Instructor James Williamson examines popular web development tools, server-side software solutions, content management solutions, and cloud-based software, providing a high-level overview of the world of Web publishing.
Okay. I'm sure that most of you probably know what a URL is and that it stands for Uniform Resource Locator. However, did you know that the URL is actually made up of several parts and the syntax used within it determines what type of file you're looking for, where to find that file and it allows you to pass along several optional parameters to the server? Well, let's start by examining a common URL and identifying the different parts of it. If I type http://www.lynda.com into my browser, it navigates me to the homepage of lynda.com, just as you'd expect.
The first part like the link, the HTTP, is known as the protocol. We'll discuss protocols in more detail later. For now, it's enough to know that the protocol tells the server what type of file it is requesting. There are many protocols and you need to be sure your URLs are using the right protocol, based on your file type. The HTTP protocol, for example, is used primarily to transfer HTML files. The second part of the link, the www.lynda.com, is known as the resource name and it is also made up of several parts.
The two forward slashes are for correct syntax only and their inventor, Tim Berners-Lee, has previously said he now regrets making them part of the syntax, adding that, "It seemed like a good idea at the time." The resource name is identified by a series of domains, separated by periods between them. In this example, the www is the subdomain, lynda is the domain name and com is what we call the top level domain. In many cases, the subdomain is no longer required, which is why you could also type in lynda.com without the www and still arrive at the same page.
Most web servers are now instructed to redirect to the default subdomain if none is provided, giving us the freedom of not having to type out the entire www syntax. However, this is not always given. So, when creating your URLs, you should know whether this is allowed or not. So, what is a subdomain, anyway? Well, in the simplest sense, it's simply a folder that your web content is located at. Most web servers serve multiple types of content and subdomains allow servers to identify unique sites or unique areas of content.
www has evolved as the default subdomain for most web content. When you upload your site to your server as you publish it, chances are you're looking for the www directory. There are many subdomains beside www, such as FTP or video. In fact, the server administrator can create as many subdomains as they wish. So, in theory, this could be almost anything. Now turning our attention back to our link, the lynda portion of our URL is known as the domain name. This is the name that the browser uses to check with the web server to see if this site exists or not.
We'll learn more about that process when we discuss domain name servers, or as they're more commonly referred to, DNS. The .com is a top level domain and is also tied into the DNS system. This is the name server that your browser will use to resolve the location of the site you're requesting. Common top-level domains are com or an edu, although that is by no means all of them. Now it seems like we've examined every part of our example URL, but, in fact, there are a couple of parts of it that we've left off.
A URL should also specify the path on the server to the requested file and which port on the server that you should connect to. In this case, both of those requests are left off, which means that both will get the default values for the server. It's a rare to see a port definition within the URL and most servers default to 80. Unless you are instructed otherwise, it's almost always safe to leave the port number off the URL. The port is appended to the end of the top-level domain and proceeded by a colon. So, we could type in, http://www.lynda.com: 80 and there you go, we get the same result.
Every site has a default page and that's often referred to as the homepage. This is typically a page named index.htm or default.htm, but in reality, the server can set any pages it wishes as the default page. Note if you type in www.lynda.com, the URL resolves itself to www.lynda.com/Member.aspx. In the case of lynda.com, Member.aspx is the default page and as such, doesn't have to be added to the URL in order to have the browser navigate to it.
Of course, if we need to, we can tell the browser exactly which page to browse to. Let's say we want to sign up for the lynda.com newsletter. If we change the URL, here we go, to www.lynda.com/news/newsletter.aspx, here we go, The path of the URL is now /news/newsletter.aspx. This tells the server to find the news directory and locate the newsletter.aspx inside of it and there it is.
Now, finally, we can also use the URL to pass parameters to the server to refine the information retrieved by the server. If we change the URL to this really long string, I'm not going to read out, just notice the end of it and what's been added to it. The ViewCourses page is filtered to display only my videos within the lynda.com OTL and you can see that in the page here. Now, note the Question Mark that comes after the path. This tells the server that additional information is on the way. The lpk1 and 128 are what we call name value pairs.
The lpk1 identifies to the server that we want to filter by authors and the 128 is my unique author ID. Of course, to know the correct name and value pairs, we'd have to know the name that represents an author within the database and we'd have to know my unique author ID. It's unlikely that any user is going to know that information. So, most additional parameters are passed on to the form submittal, the user clicking specific links or other automated means. Now when resolving URLs, you may hear the term absolute versus relative.
An absolute URL is a unique URL that contains the entire file path, including the protocol, http://www.lynda.com is considered an absolute link and will work no matter where the user is currently. A relative link points the resource from a current reference point, usually within the same domain. So, if you create the URL news/newsletter.aspx, that would assume that you are in the same directory.
Look inside the news directory and locate the newsletter.aspx file. Absolute URLs are typically used to link outside of the domain or website, while relative links are typically used within the same domain.
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