This navigation panel appears when you have used a presentation template rather than a web template.

Slide navigation

On any slide of the Presentation on the Web if you move your mouse to the lower left corner of the browser window, you get a pop-up page navigation control that includes a menu of all slides, thus allowing direct jumping to any slide.
Previous, Home and Next controls as well as a pop-up menu showing all pages of a Presentation.
I am not aware of any method to remove this new feature from presentations.