We consider divergence form elliptic equations Lu := ∇ · (A∇u) = 0 in the half space R n+1 + := {(x, t) ∈ R n × (0, ∞)}, whose coefficient matrix A is complex elliptic, bounded and measurable. In addition, we suppose that A satisfies some additional regularity in the direction transverse to the boundary, namely that the discrepancy A(x, t) − A(x, 0) satisfies a Carleson measure condition of Fefferman-Kenig-Pipher type, with small Carleson norm. Under these conditions, we establish a full range of boundedness results for double and single layer potentials in L p , Hardy, Sobolev, BMO and Hölder spaces. Furthermore, we prove solvability of the Dirichlet problem for L, with data in L p (R n ), BMO(R n ), and C α (R n ), and solvability of the Neumann and Regularity problems, with data in the spaces L p (R n )/H p (R n ) and L p 1 (R n )/H 1,p (R n ) respectively, with the appropriate restrictions on indices, assuming invertibility of layer potentials for the t-independent operator L 0 := −∇ · (A(·, 0)∇).