Leftside Back for Chrome
More About Leftside Back
Due to security restrictions, the extension is not working in the chrome webstore. So to test the extension simple navigate to another website, where everything should work fine :)
This extension turns your left side of your browser window into a large back button. It allows you to navigate back by just hitting the mouse on the left side of your screen. You can configure whether to add a visual arrow on the left side when hovering and the amount of pixels from the left side which should be used for the back button functionality.