The content below is simple, but not how items are grouped in the main and which heading levels are used. Remember, sections, asides, and articles are semantic containers, and semantic containers require headings. Each section below has a border added to help you see the grouping on the page. Outer section borders are maroon, nested section borders are gray.
HTML
HTML defines a webpage's structure and content.
HTML Tags
Some HTML tags use an opening and closing pair of tags to surround content. These wrap around that content and help to define what it is. Others only require a single tag for markup. Those are called void tags.
HTML Attributes
In HTML, attributes are always added to the opening HTML tag in the pair. If there is no closing tag, the attribute will be placed in the void tag itself. All attributes should be added with lowercase letters and double quotation marks where needed.
CSS
CSS specifies a webpage's layout and visible appearance.
CSS Selectors
In CSS, you can change the appearance of elements on your pages to make them more pleasing to look at and use. CSS selectors allow you to target the elements on your page by tag name, attribute, relationship, class, ID, and more.
JavaScript
JavaScript describes a webpage's dynamic behaviors and actions.
When to Use JavaScript
Generally, you want to use JavaScript only when necessary, to improve user experience. Many companies and IT teams will disable JavaScript on their websites, so your sites should be functional without it.
JavaScript Libraries and Frameworks
Today, many job postings will list a desire for experience with specific JavaScript frameworks or libraries rather than asking for experience with JavaScript itself. This doesn't mean that you don't need to learn it! Understanding the language these libraries and frameworks are built on, makes it easier to learn them as needed.