If you have a formula y = f(x0, y0, x) which expresses the solution in terms of the initial condition, you can plug it in the applet and see if blue curves (numerical solutions) coincide with red curves (obtained from your formula). You can also use this method to verify whether your formula holds for some particular initial conditions.
View Instructions on using the Applet
Marek Rychlik (email@example.com)
Author's Home Page: http://alamos.math.arizona.edu