How do I hide the navigation bar on safari, chrome, and firefox

In El Capitan (10.11), the menu item of interest is the first in the View menu: “Always Show Toolbar in Full Screen.”

Uncheck this menu item and the entire screen will be devoted to the web content until the arrow is brought to the top of the screen.

Using Full Screen Mode will maximize usable screen real estate. On Safari, click on the Green "traffic light" button.

I believe that the only way to get any of the three browsers to behave the way you would like is via an extension.

In Safari, in the View menu, try "Hide Toolbar".

Firefox Support

Chrome Support

For that to happen, you are not doing what I said. But, anyway, experiment with the Safari View menu to see what is possible.