I found an applet on http://mathinsight.org/applet/function_iteration_cobweb_combined. I'm going to talk about it a little bit and then embed it here. This should allow you to fiddle with cobwebs a little easier.

The left frame shows the cobweb diagram (horizontal axis y or "input" and vertical axis z or "output"). In blue is the reproduction function (z=f(x)) derived from the difference equation (x_{n+1}=f(x_{n})) and in red is (z=y). You have the ability to enter in a new reproduction curve and initial condition but make sure you hit Enter for the changes to take effect. Tapping the iterate button will start the difference equation by plotting (x_n) one at a time. Hitting reset will clear stuff and in the upper right you have navigation controls. The right panel is a time series for the difference equation showing you the same data, but as it would appear as collected data.