Axes position is changed during rendering


I have a little problem.

On figure I have 2 Axes created by
        fig = plt.figure(figsize = (16, 10), facecolor='w')
       ax1 = fig.add_axes([0, 0, 1, 0.1])
       ax2 = fig.add_axes([0.1, 0.19, 0.8, 0.72], autoscale_on=True)
There are some text and images on it:
       drawing on ax1 and ax2
       ax1.imshow(arr, extent=[0.01, 0.29, 0.1, 0.95])
       ax1.imshow(arr, extent=[0.75, 0.96, 0.5, 0.8])

My problem - when I plot the figure - ax1 changes it's geometry.
        print 'ax1:', ax1
        print 'ax2:', ax2

        print 'ax1:', ax1
        print 'ax2:', ax2
        print 'ax1 position changed during Why???'


  ax1: Axes(0,0;1x0.1)
  ax2: Axes(0.1,0.19;0.8x0.72)
  ax1: Axes(0.470649,0;0.0587025x0.1)
  ax2: Axes(0.1,0.19;0.8x0.72)
  ax1 position changed during Why???

On resulting plot ax1 has position (0.470649,0;0.0587025x0.1), but
desired are (0,0;1x0.1).

Could anyone help me, or give an idea, why axes is moved, or give an
advice, how to resolve this situation.

Thank you