The default style for this page is given by the rule
body {color: black; background-color: white; }.
This is a test paragraph. When I press on the link below, it will
be placed in the class "inv". This class has the style rule
.inv {color: white; background-color: black; }.
If it is already in the class inv, it will be placed out of the class inv.
javascript:toggle_class('body','inv')