Add a empty page template with just a header and footer section and a
„naked“ content section in between. The content comes without any
markup so you can add your own markup to the page. Good for landing
pages or other pages which needs to use another markup besides the
default stuff.
Adding class="customclass" after post_class() inserts a _second_ class-attribute, which will neither work as expected nor validate.
For multiple classes, an array with the classes needs to be constructed.
Solution added.