How Does CSS Work?

CSS, or "Cascading Style Sheets," is a programming language used to style and layout webpages. It can be used to change the size, spacing, colour, and font of content, as well as add decorative elements like animations or divide content into columns.

A Deeper Understanding of CSS

CSS, as a styling language, defines how users view documents, from layout to style. The affected documents are typically text files with structure provided by a markup language, the most common of which is HTML, though XML and SVG are also popular. CSS converts the text file into a usable form in order to present the document to the user. This presentation occurs on a computer screen, printer, or projector when using browsers.

Impact of CSS on HTML

Since both HTML and CSS have a strong influence on how information appears, it's critical to understand how CSS affects HTML. To put it simply, web browsers use CSS rules to determine how a document should be displayed.

CSS rules can be created in a variety of ways. It is possible to do so using a set of properties, each with a value that changes how the HTML content is displayed. For example, a set of CSS properties may specify that the element should have a yellow background and a width that is 20% of the parent element's width.

CSS rules can also be created using selectors. Selectors, as the name implies, choose an element or elements to apply to updated property values, such as the selector applying CSS rules to every paragraph in an HTML document. The CSS rules are stored in a stylesheet, which determines the appearance of the webpage. The typical CSS syntax becomes obvious after some practise and training.

We'll go over a basic example of CSS code with two rules below:

The h1 portion at the start of the first rule indicates that the CSS code's stylistic elements apply to anything labelled in the HTML. CSS code contains three distinct properties, each with its own set of values in the form of a pair known as a declaration. The first indicates that the text will be yellow, and the second that the background will be blue. The final property adds a 1-pixel wide solid border around the header. In the preceding example, the second rule applies to HTML elements labelled because it starts with p This rule is fairly straightforward, as it simply changes the text colour to orange.

Keep in mind that most websites have more content and more rules, but the example above can help you create your own CSS. The best way to accomplish this is to use basic HTML with a paragraph and header. You might also want to experiment with list elements (li> and ul>) to include more sets of rules in your CSS. If you want to be a pro at web development, then take a online web development course.

How CSS Works

After loading and parsing the HTML content and CSS styling, the process of combining them takes place in two stages. The browser first converts them to the Document Object Model (DOM). The browser will display the content once the DOM has combined the content and style of the document and is a representation of the document within the computer's memory.

Understanding the DOM

CSS's functionality is heavily reliant on the DOM. Nodes form tree-like structures in DOMs. Every text, attribute, and element in a markup language (such as HTML) will become its own DOM node.

The relationship of each node is defined by how it is connected to other DOM nodes, which can be child nodes, parent nodes, or sibling nodes. Because this is where the document's content and CSS meet, a thorough understanding of the DOM will better equip you to maintain, design, and debug your CSS.

Consider the HTML below:

The node that corresponds to the HTML's p> element will be a parent within the DOM. The children will include text nodes as well as those that correspond to span> elements. Each span> node also functions as a parent, with text nodes as children. The HTML snippet above will be interpreted by the browser as the DOM tree below.

P

├─ “Let’s say:”

├─ SPAN

| └─ “Hello”

├─ SPAN

└─ “World”

Without any CSS code, the browser would simply interpret the HTML snippet as plain text via the DOM, displaying "Let's say: Hello World" with no colour, font, or style changes.

Applying CSS to the DOM

Continuing with the previous example, your CSS class can demonstrate what happens to the DOM and the resulting display when you style the document with CSS. Using the same HTML snippet as before:

Use the following CSS:

According to the preceding explanation, the browser will begin by parsing the HTML. This process will result in the creation of the above DOM from the previous section, followed by the parsing of the CSS. The CSS only has one rule, which employs a span selector. As a result, that rule will apply to every occurrence of in the HTML, which is two.

Instead of a simple plain text of "Let's say: Hello World," it will have stylistic elements attached: each "Hello" and "World" will appear in a box with an interior colour of red and a border that is a solid pink line and 1 pixel thick, thanks to CSS. If you are interested in CSS and want to know how much you know about CSS, then you should try the online CSS quiz to test yourself.

Methods of Applying CSS to HTML

There are several methods of applying the CSS code for stylistic changes to HTML.

•  Via External Stylesheets

An external stylesheet is created when CSS code is placed in a completely separate file. The file has a.css extension and is referenced in the HTML by a link> element. Because of its versatility, many programmers strongly prefer using an external stylesheet. Because a single stylesheet can be used to set the style and layout of multiple documents, future changes only require a single update.

• Via Internal Stylesheets

An internal stylesheet is another way to apply CSS to your HTML. Instead of putting the CSS in an external file, you put it in the HTML head, where it sits within a tag. This method is extremely useful in certain situations. A content management system or another programme that does not allow direct modification of CSS files is one example. Using internal stylesheets to add styling is inefficient. In the case of a website, the CSS would have to be repeated on each page. If you wanted to change something, you'd have to do it on each one. In contrast, you could link the same external stylesheet on multiple pages and change only one location for widespread style changes.

• Inline Styles

Inline styles are CSS declarations that affect a single HTML element. Inline styles, as opposed to internal stylesheets, are stored in a style attribute rather than a style> element. When possible, experienced developers avoid this method because it requires them to update identical information multiple times in a single document and makes CSS coding more difficult to understand and read.

Instead, it is preferable to separate different types of code, which will be useful during the development and debugging processes. Furthermore, anyone who uses the code in the future will find it much easier to grasp. The only time using inline styles for CSS makes sense is if you work in a highly restricted environment. This method would be used, for example, if you could only edit the HTML body and nothing else.

Conclusion

If you're interested in learning more about webpage styling, you can enrol in a CSS bootcamp to learn more about the interactions between CSS, HTML, and DOM, as well as additional CSS application methods.

Read more:What is CSS and its use?