The Waterstones website is hiding a cute secret advert for books in its source code. “Interested in coding” asks a line in the site’s back-end. Books are then recommended to aspiring computer programmers, including HTML & CSS by Jon Cucket and the complete guide to the Pi minicomputer Learning Python with Raspberry Pi by Alex Bradbury.

“Source code” is the underlying computer code that web browsers interpret into the text and pictures you see when you visit a website. You can view the advert for yourself by heading to the Waterstones website and hitting CTRL + U or Option+Command+U if you’re using a Mac. But then you would know that already if you had found it…