Most of the time when I teach HTML to a group of students, they make webpages about something they are interested in - a band, recipe, place or something like that. People always have something to say, and love saying it to the public online.
Invariably (in the US at least) someone in the group picks their dog, or dogs in general. People find common ground with learning partners around animals and pets, and it intenet offers a plethora of pictures of dogs, and puppies, to include in a webpage project.
No offense of could to cats and kittens, but in my experience people more often want to showcase their dogs in my classes than cats. I don't what that says about cat vs. dog owners, but that's been my observation.