Web developer fundamentals
HTML/CSS
This is what a web page is made of. Using these tools, you can compose well designed pages with rich content in it. Web technology is all about compiling HTML and CSS (and some Javascript) and sending it to your browser.
HTML is a markup language, which means it's a syntax for marking up content. For example, this text is in a paragraph HTML element, which looks like this: <p>Hello this is a paragraph element, often referred to as a "p tag"</p>. You can see the opening and closing tags, which specify the type of element, and the content in between.