Depending on what type of graph you're looking to create, you may want to turn the gridlines on or off. The grid is automatically shown on new graphs. To turn the grid off, open the Graph Settings menu by clicking on the wrench in the upper right hand corner.
If the grid checkbox is enabled, the grid lines will be visible. You can click on the polar grid icon and cartesian grid icon to toggle between the different graph papers.
Pro-Tip: Creating an artsy graph? Turn the gridlines and axes off for an awesome, blank canvas.