  The paper considers excited random walks (ERWs) on integers in i.i.d.
environments with a bounded number of excitations per site. The emphasis is
primarily on the critical case for the transition between recurrence and
transience which occurs when the total expected drift $\delta$ at each site of
the environment is equal to 1 in absolute value. Several crucial estimates for
ERWs fail in the critical case and require a separate treatment. The main
results discuss the depth and duration of excursions from the origin for
$|\delta|=1$ as well as occupation times of negative and positive semi-axes and
scaling limits of ERW indexed by these occupation times. It is also pointed out
that the limiting proportions of the time spent by a non-critical recurrent ERW
(i.e. when $|\delta|<1$) above or below zero converge to beta random variables
with explicit parameters given in terms of $\delta$.
