Zoom Bar
This tool allows you to zoom to predefined levels on the map.
Pass the arrow cursor over the ‘Zoom Bar', click once with the left-hand mouse button on an individual bar or on the plus / minus buttons.
Choosing a bar closer to the plus sign will enlarge the map and show you more detail. Whereas , choosing a bar closer to the minus sign will show you a wider area of the map on screen, but with less detail.