Many of them are tied to the work they do at school. Others are tied to hobbies. Very soon, though, children who spend much time surfing learn that spelling counts. My kids notice that bulletin board writers with poor skills are made fun of or not listened to. When they work on their pages, they want their spelling checked.
Good pages require good writing.
School related pages don't have to be full of reports. My eleven year old is doing a pioneer page, because she loves pioneers. She is including book reports of her favorite pioneer books, quizzes, and fun facts. She may write a few pioneer stories as well, and she is working on some drawings. By the time she finishes her page, she will have incorporated most of her school subjects, and she won't even know it.