The Extra Theme includes a “Trending” feature in the top header. This feature highlights popular posts on your site by scrolling through links to your most active posts. Beside the links is a button (the three lines) which lets you pause the link scrolling. The button isn’t particularly intuitive (as three lines typically indicates a menu), so you may wish just to hide this button entirely. There doesn’t seem to be an option within Extra to hide the button, but you can easily do so with the following CSS:

/* Hide trending button */
#et-trending-button { display:none !important; }

You can add this to the theme by pasting it into the “Custom CSS” box found in the ePanel at “Extra > Theme Options > General Settings” (at the very bottom).