What is CSS? The Ultimate Intro

CSS is what adds style to a website. Without CSS, web pages would be in plain text, on a white background, and very difficult to use! CSS builds on HTML to create the visuals you see on websites every day.

What does CSS stand for?

CSS stands for Cascading Style Sheets.

What is CSS? 

CSS is what adds style and colour to every webpage. While HTML controls the structure of a document with paragraphs, headers and images, CSS allow you to specify colours, fonts, layouts and more. If we think of a web document as a human body, HTML is the head and the body. CSS would be the style of that. For example, the colour of our eyes, the size of our ears, the pigment of our skin, and even the clothes that we wear. In other words – it’s our look and style. To offer some perspective, Javascript would be the equivalent of how we interact with people. How we talk, shake hands, wink, nod our heads, etc.

How does CSS work?

CSS Selectors

A CSS Selector is what we use to target HTML on our web pages that we intend on styling. A Selector is part of a CSS Rule that informs the browser where CSS is implemented on a page.

CSS rule

A CSS rule is made up of one or more selectors and a semicolon-separated list of declarations inside brackets. Each declaration has a property and the value separated by a colon. A rule is made up of one or more selectors. In the example below, the selector is a paragraph element represented by the letter P. This means that the rule will apply to all paragraphs. This declaration states that the text colour inside a paragraph will be teal. Note the spelling of “color”.

p {color:teal}

For more information on how to use CSS to style your HTML, see our helpful guide.

What is a CSS file?

A Cascading Style Sheet file is an extension that formats our web pages. Different files give different styles to elements on our sites and applications. A CSS file can be like a template that holds customised properties for how to style the HTML elements of a website. 

CSS files are used by designers to maintain a similar style throughout an entire website. The file stores the properties for each page of the site within one place. This is incredibly useful when you are designing or redesigning a website because it means that you do not have to individually style each page.

You can quickly and easily target one, some, or all, specified elements on a single page or even all pages on the site.

With it, you can target the elements you want potentially from a single location. If you make any changes, they will then proliferate out to the page or pages. If you need to edit the style, you can do so from a single location and the targeted elements immediately reflect that change. Interestingly, you can also apply different styles depending on the device on which your content is to be viewed. You might reduce the dimensions of elements for viewing on a smartphone, then increase them when viewed on say a laptop or a desktop.

External, Internal & Inline CSS

CSS can be used in three ways – Inline, Internal and External. Here’s the difference between the three.

• What is External CSS?
  External style sheets are very useful, especially when you want to maintain one style throughout an entire site. The style rules need to be created just once and they are applied to all required pages within a site. If you need to change the style slightly on all pages that use this external sheet, then it just needs to be changed once and it automatically applies to all pages – which is handy! In general, this is the standard way of using CSS.
• What is Internal CSS?
  This applies to just the page that you are working on. This can be used if a unique style is required for one page of your web app.
• What is Inline CSS?
  Inline CSS, which I will be using in the example below, relates to a specific page element. In the example below, we use CSS to turn a heading to the colour red on a page. You’ll notice that the order is embedded within HTML text – which is how it is written. However, Inline CSS is only used where you want to apply a unique style to one element.

<!DOCTYPE html>
 <html> 
 <body> 
 <h2 style="color:red;">This is a Red Heading</h2> 
 </body> 
 </html>

The front end of the code above will eventually look like this:

This is a Red Heading

Where can I learn CSS?

There are many resources available that can teach you CSS. Code Institute teaches it as part of our Full-Stack Development programme. If you want to learn some of the basics for free, then try our free 5 Day Coding Challenge. After just one hour a day for five days, you will have built your first-ever web page. Register today through the form below and take your first steps in becoming a coder.