Filling any empty cells with the value above
For those not requiring VBA for this, select ColumnA, Go To Special..., Blanks and:
Equals (=), Up (▲), Ctrl+Enter
should give the same result.
Given you asked for VBA, there is a quicker way than looping (the VBA equivalent of what pnuts posed above, with the additional step of removing the formula at the end):
On Error Resume Next
With Selection.SpecialCells(xlCellTypeBlanks)
.FormulaR1C1 = "=R[-1]C"
.Value = .Value
End With