Bert's blog

How this web page works

The end of yet another busy week, so this week’s post will also be short. I will give a brief overview of how I experienced web development over the last two decades and outline how this particular web page works.

A brief history of web development

When the world wide web first started being used on large scales, people that wanted to provide content and people that wanted to view content decided on a general standard for encoding and displaying web pages. This standard is called HyperText Markup Language (HTML) and was first introduced in 1993. It has evolved quite a bit since then, but is still in use. So every web application, no matter how complicated its inner workings, will generate web pages using HTML and every browser, whether it is running on a computer, phone or tablet, will know how to interpret this HTML. In principle that is; everyone that ever got involved with serious web development will know that HTML support is not as uniform across different browsers as it should be.

At first, HTML was used to generate the entire web page, including all colours, fonts and layouts. However, it became clear very quickly that this posed an unwanted overhead: many pages can share the same styling and only differ in content, and adding all the markup code for the styling to each and every one of them makes these pages unnecessarily heavy. On top of that, if the styling would be hard-coded in every page, it becomes very hard to change the style without having to edit every single page. The community therefore decided to explicitly separate content and styling: HTMl would be primarily used to contain the structure of the web page and the content that changes between pages, the styling would now be done using a new styling language, called Cascading Style Sheets (CSS). This paradigm still stands: a modern web page will usually consist of many HTML pages containing content, and one (or a few) CSS style sheets that encode the web page style. A well designed web page can change its outlook completely by simply changing the style sheet, without requiring any changes to the HTML. Real web pages often still contain some hard-coded styling within the HTML, despite this now being considered bad practice.

Both HTML and CSS deal with static web pages, i.e. web pages that require no user interaction and do not change over time. This is obviously not the only type of web page used nowadays. If you e.g. click the Contact button in the top right corner of this page, a popup will appear that allows you to submit a message to my email. If you then close the popup by clicking the cross in the top right corner, the popup disappears again. All this interactivity needs to be scripted, i.e. requires a set of programming commands that tell the browser how to behave when specific actions are executed by the user that is viewing the web page. The standard that was developed for this is called Javascript. It was loosely based on the Java programming language, but is not really related to it. While Javascript allows for the creation of very complex interactions, it is ultimately the browser that performs all the tasks and that is why we call it a scripting rather than a programming language. As with the styling, a set of web pages usually contains a single Javascript engine that is shared among the various pages and that can be edited separately.

The triad HTML, CSS and Javascript forms the backbone of all modern web pages. Other content like videos, images and audio is much less standardised, and older technologies like web applets are generally no longer used. This means that any web page you visit nowadays will somehow be using HTML, CSS and Javascript to generate whatever you see and interact with. The real technology is contained in how these web pages are generated before they are presented to you.

Servers and clients

The first HTML pages were simple text documents that contained an entire web page. When a user tried to access them through their browser, the browser had to simply request that page from the server where it was stored and then load it. The server simply stored all the pages on its file system, and its only task was to reply to page requests.

When web pages grew in complexity, it became apparent that this way of serving web pages is not ideal. Many web pages contain a lot of content that is static (i.e. does not change from one page to another), like navigation links, copyright banners… and relatively little content that actually changes. Storing all static content for every single page causes a lot of overhead. Things got even worse when people started using web pages where content is generated by web page users, like online forums or social networks. These web pages use a single layout to contain a large amount of different content and in the case of social networks, this content even depends on the user that is accessing the web page.

To deal with this changing demand, the role of the server was reevaluated. From the browser point of view, it makes very little difference whether the server replies to a page request by just loading a file from its hard disk and sending it to the client that requested the page, or by generating a new page on the fly based on the contents of different files on its hard desk. In other words, the client browser does not care whether the file it requests actually exists when it requests it, as long as the server replies by providing an actual file. From the server point of view, there is clearly a significant difference between these two actions, as one is more straightforward than the other. However, since the main time cost of a web page request (i.e. how long it takes for the client to receive a page after it sent a request to the server) depends mostly on the network speed (which is relatively slow), both ways are generally equally efficient. Instead of a simple file sending program, we can hence run a file generating program on the server and generate files as they are requested, possibly based on the details of the person that requested them.

So while the end result is still HTML, CSS and Javascript, many web pages nowadays run server-side software that actually generates the HTML (and sometimes CSS and Javascript) whenever a page is requested. The actual content of the web page can then be stored in much more efficient ways, e.g. in a database. Many web pages from the 2000s were written using a combination of PHP (a server-side scripting language) and MySQL (a server-side database). I know this because I have some personal experience with this. Later, developers started using more complex client-server interactions like AJAX, whereby client-side Javascript sends interactive requests to the server-side software to provide fully interactive web pages. I am not sure, but I think this is still how large social networks like Facebook work.

The success of server-side web pages comes with a downside: as these server-side applications get more and more complex, the load on the servers becomes very high. Furthermore, the use of server-side databases makes web pages very complex and hard to maintain without access to the server. In other words, server-side applications are good when you have your own server and a lot of resources behind that server. They are not ideal for small web pages, especially when those web pages don’t really require the power of a server-side application.

That is why a new paradigm developed over the last few years. I’m not entirely sure about the timing here; when I was into web development around 2010 server-side application where definitely still a thing, but when I checked again about 3 years ago this new paradigm had clearly started. The new paradigm reduces the load on the server again and moves the CPU intensive part of the web page back to the client by a more extensive use of Javascript. The overhead of static elements that are shared between pages is no longer seen as a real issue: this overhead is heavily reduced by compressing the relevant HTML (and CSS and Javascript) and is acceptable on the server-side, where data storage is cheap and processing power is expensive.

Many small, mainly static web pages (like blog systems) are now typically generated by a static generator, for example Jekyll. The generator works a bit like the server-side scripting engines like PHP and combines elements from different locations into the final HTML pages. These final HTML pages (and CSS and Javascript) are then copied onto a server from where they are served like in the old days. The real power comes from the integration of these static generators within existing repository systems like GitHub. The source code for the static web pages (written in Jekyll) is stored in a git repository, and whenever this repository is updated, a web-based static generator is invoked and transforms the source code into the actual web pages that are then moved to the server from which they are accessible. GitHub automatically creates such a web page for all of its projects, see GitHub pages

Static web pages sometimes need interactivity similar to that of AJAX-based systems. To support these, lots of web-based services are available that provide very specific low-level functionality, like handling form submissions or providing comments sections to embed within a blog system. A web page is hence more and more a puzzle made up of many dedicated building blocks.

This web page

This blog system is written in Jekyll, and is hence stored in a GitHub repository as a number of layout files and a large number of posts, written in MarkDown, that only contain blog content.

Whenever I finish a post, I simply add the post file to the repository and push to the remote repository. This triggers a webhook that connects to netlify. The web service running there fetches the latest version of the repository, runs the static generator on it, and then stores the resulting web page on the netlify server system, from where it is then visible as

So for me, writing a blog post is now as easy as writing a text file (in my favourite text editor: nano), adding that text file to a git repository, and doing the same git magic I do every day for my software development. Everything else happens completely automatically.

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