That is most likely because you need to have the file extension .php on a page where actual php will be run.
Change your file extension from .html to .php within the files tab and it should run it correctly.
Something else I noticed is that you are missing your <html>, <head> and <title> tags. I assume those will be added when your includes start working, but if not, that will need to be fixed. You also have other html errors throughout the document. Once you get it changed over to .php and the includes start functioning, be sure to run the final output through the html validator here to clean up any other problems: