A lot of websites nowadays, admittedly more so in desktop view, (which is now seen by fewer thanks to the world of mobile) hide the navigation bar when you scroll down. This is a good thing as it reveals more of the page without the distraction of menu items you do not wish to see for the time being. Whilst the navigation is very important, the content is arguably more important. The menu is then shown again when the user scrolls up.
This all seems fair enough. When the user scrolls down, we assume that they are reading the contents of the page. If the user does not scroll, then the page's content does not extend beyond
100% of the height of the viewport, therefore the menu is not hidden (as they have not scrolled).
What I do not understand though (we will get to my question eventually :-) is that these site's do not show the navigation when you go to click or where you
hover where the menu would be. You physically will have to scroll up before you see the navigation bar again. This seems like such a schoolboy error, but a lot of websites are doing this. Not showing the nav bar unless you scroll up.
I am assuming a worse case scenario, that the user is 'super thick', and that they may think that the site is broken.
"When I take my mouse to the top/right/left of the screen the menu does not appear?"
I do not think it is too realistic to assume that they will say the above; conclude the site’s functionality is not providing them with what they need and go elsewhere.
Do we therefore think that the menu should be shown even when (we think) the user is about to ask for it?