I feel like I need to rant a bit on chapter 18. First of all it is probably the first chapter in the whole HTML CSS series that was not easy to understand (so I guess good job on the previous ones). Especially that "it's then positioned in relation to the first parent element it has that doesn't have position: static" part. Most importantly after we do some changes the conclusion in the next chapter says "That's absolute positioning at work". The thing is absolute positioning had nothing to do with the changes, it was "margin" command. I can go back and delete "absolute" commands and it will have zero effect.
I suggest rewriting that chapter.
P.S. next (19th) chapter isnt better. Again the positioning command makes absolutely no difference, margin does all the work. Very poor illustration of how the property works.
P.P.S I finished the lesson and have to say all chapters after 18 are pretty bad. HTML positioning is not covered at all.