World Wide Web
Introduction
Understand how computer networks can provide multiple services including the Web. I'd say that HTML would fit here - Miles.
Self study resources
O2 Learn to Code. Nice interactive tutorial for HTML and CSS from Decoded, in the style of Codecademy.
Shay Howe's Beginner's Guide. Goes further than the above, and non-interactive. I wonder if this might be only appropriate at secondary.
Excellent structured course on HTML and CSS, which also addresses networking ideas from Codecademy: includes slides and interactive exercises.
Resources for lectures or group study
Thimble. Lovely (free) web-based HTML editor for creating web pages by hand.
Coffee Cup Free Software HTML Editor
Explore 'Top 10 Infographics about the Internet' from TechCreak: Facts and Figures, Computer Performance, A Day in the Internet, What happens in in an internet minute? Then make your own infographic with Piktochart.
John Naughton on 25 things you might not know about the web.
Resources for use with pupils
Thimble. Lovely (free) web-based HTML editor for creating web pages by hand. Some pre-built projects make this great for use in schools too.
Coffee Cup Free Software HTML Editor
Hackasaurus Goggles. Like Thimble, also from Mozilla, but can be used with younger children to provide some insight into HTML through modding existing pages.
How the Internet Works A module aimed at Year 5 with activities and resources.