  Frequency dependent exchange correlation kernels for time-dependent density
functional theory can be used to construct approximate exchange-correlation
potentials. The resulting potentials are usually not translationally covariant
nor do they obey the so-called zero-force condition. These two basic symme-try
requirements are essential for using the potentials in actual applications
(even within the linear re-sponse regime). We provide two pragmatic methods for
imposing these conditions. As an example we take the Gross and Kohn (GK)
frequency dependent XC functional (Phys. Rev.Lett. 55, 2850 (1985)), correct
it, and numerically test it on a sodium metal cluster. Violation of the basic
symme-tries causes instabilities or spurious low frequency modes.
