How to remove sub surf on z axis? I am really new to Blender, so please bear with me here.  I was trying to make a Starbucks cup, so I needed to get a round-edged plane (for the middle part of the cup).  I got help from a friend, who told me to subdivide the plane, then use a subsurf modifier to create the rounded edges.  All is good and fine on 2D, but when I extrude to create the height of the cup, I get this weird thing:



I think this is because the subdivision surface is being applied to the z-axis too, but I don't really want that.
Can I apply the sub surf to the x and y without affecting the z?  Again, please excuse my ignorance.  Any help would be appreciated.
No you cannot, subsurf applies to the whole mesh evenly in all directions.
What you need is to learn how to use what are generally called "control loops". 

Control loops are extra edges you add to your geometry to keep subdivision surface from rounding out parts of the mesh you don't want to be smooth or curved. You can add them using Ctrl + R



Also consider a simpler method using the screw modifier since you are creating a simple revolution geometry