The “unofficial” C For Dummies site has been online continuously since 1997. It was written to support the original two-volume book, C For Dummies. That book has been through several variations over the years, with the web page providing support during that time.
Beginning Programming with C For Dummies was published in 2013. This site was revamped in April of that year and the first blog post was made. When the book became available in July 2013, the blog went live and the current site update was unveiled.
New Lessons are added every Saturday, with new Exercises added on the first of the month and solutions posted a week after.
The site is “unofficial” because the publisher (Wiley) owns the rights to the title and its contents. Their webpage offers the official support, though this site is updated far more frequently.