On a MacBook, you scroll up and down by swiping two fingers on the trackpad. In recent versions of OS X, however, including OS X Yosemite, Apple changed the way the trackpad reacts to scrolling gestures. Where you used to swipe up to move up, now you swipe down. If you don't like this method of scrolling, you can click and drag the scrollbar to scroll. You can also change your scroll settings using the System Preferences panel.
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Scrolling Up Using the Trackpad
To scroll up on a MacBook running OS X Yosemite, place two fingers on the trackpad and slide them downward. The content tracks the movement of your fingers. Think of this method as if you are grabbing a piece of paper and sliding it. To look higher up on the paper, you slide the paper downward so that the top is in your field of vision.
Scrolling Up Using the Scrollbar
Depending on the application you're using, you may have access to a scrollbar at the side of the application window. In OS X Yosemite, the scrollbar is hidden by default, but it's still there. Start scrolling using the trackpad to reveal the scrollbar on the right side of the window. Once the scrollbar is visible, you can click and drag it in the direction you want to view. To scroll up, drag the scrollbar slider up. You can also use an external mouse to click and drag the scrollbar slider.
Changing Trackpad Scroll Settings
Use the Trackpad Preferences panel to change the way the trackpad behaves. Click the "Apple" menu in the top corner of your MacBook's screen, select "System Preferences" and then click the "Trackpad" icon. Select the "Scroll & Zoom" tab to configure scrolling options. To revert to the old way of scrolling in OS X, remove the check mark from the "Scroll Direction: Natural" check box.
Changing Mouse Scroll Settings
If you have an external mouse connected to your MacBook, use the Mouse Preferences dialog to change how the mouse scrolls. Click the "Apple" menu in the top corner of your screen, select "System Preferences" and then click "Mouse." If you have an Apple Magic Mouse connected, you are presented with the same set of options as in the Scroll & Zoom section of the Trackpad settings dialog. Remove the check mark from the "Scroll Direction: Natural" box to revert to the old method of scrolling in OS X. If you have a mouse with a scroll wheel, adjust the "Scrolling" slider to modify how quickly the mouse pointer moves when you use the scroll wheel.