We study the mass, the mixing and the coupling with Z boson of the lightest
Higgs boson in the next-to-minimal supersymmetric standard model. The vacuum
structure of the Higgs potential is analyzed and the new false vacua are
discussed. The significant parameter region can be excluded by requiring that
the realistic vacuum is deeper than false vacua, which result in constraints on
the properties of the lightest Higgs boson.Comment: 23 pages, 8 figure