While there's some good basic stuff here, I'm not a fan of the layout. They talk about responsive design, but use a very thin column for the main content, leavi

While there's some good basic stuff here, I'm not a fan of the layout. They talk about responsive design, but use a very thin column for the main content, leaving an ocean of blank white space on either side, at least on desktop. I'm also taking issue with their advice to "disable viewport zoom" for mobile sites, which is not cool. There is no need to disable zooming for your responsive site to load and display correctly. Taking away the user's right to pinch and zoom is an accessibility issue. If you're learning HTML and CSS, I would suggest you ignore their advice to disable zoom. Your viewport meta tag should be something like <meta name="viewport" content="width=device-width, initial-scale=1" /> but you shouldn't be adding "maximum-scale=1.0" to that, because it prevents pinch and zoom.