  In this paper we developed approach based on the BFKL evolution in $\ln\Lb
Q^2\Rb$. We show that the simplest diffusion approximation with running QCD
coupling is able to describe the HERA experimental data on the deep inelastic
structure function with good $\chi^2/d.o.f. \approx 1.3$. From our description
of the experimental data we learned several lessons; (i) the non-perturbative
physics at long distances started to show up at $Q^2 = 0.25\,GeV^2$; (ii) the
scattering amplitude at $Q^2 = 0.25\,GeV^2$ cannot be written as sum of soft
Pomeron and the secondary Reggeon but the Pomeron interactions should be taken
into account; (iii) the Pomeron interactions can be reduced to the enhanced
diagrams and, therefore, we do not see any needs for the shadowing corrections
at HERA energies; and (iv) we demonstrated that the shadowing correction could
be sizable at higher than HERA energies without any contradiction with our
initial conditions.
