  Measurements of the $IV$ characteristics of site-diluted Josephson-junction
arrays have revealed intriguing effects of percolative disorder on the phase
transition and the vortex dynamics in a two-dimensional XY system. Different
from other types of phase transitions, the Kosterlitz-Thouless (KT) transition
was eliminated with the introduction of percolative disorder far below the
percolation threshold. Even after the KT order had been removed, the system
remained superconducting at low temperatures by establishing a different type
of order. Near the percolation threshold, evidence was found that, as a
consequence of the underlying fractal structure, the critical dynamics of the
phase degrees of freedom persisted down to zero temperature.
