The left and right navigation panels can be enabled or disabled from showing on the login page.
The navigation panels for the login page can be managed on the right side of the control panel under Master Settings Edit Login Page
Under the 'Edit Login Settings' section choose the desired option from the 'Login Page Nav Panels' drop down menu.
The options include showing both the right and left panels, showing only the left or the right or not showing either the left or right panels.
Click on the button