In the fifth and only exercise of mid section, retrieve the content of exercise for an ADD active just
after the body tag, which is expected to gather all the contents, associate into them a height in
the stylesheet, then define the height of the header, modify the background color, given it a hexadecimal
value, and select a phone to apply to the stylesheet.
Finish the exercise, inserting an inner margin to all the tags which do not have one.
Once done this, go back to the lessons and get on with completing the section.