  We present results of inelastic light scattering experiments on
single-crystalline La$_{2-x}$Sr$_{x}$CuO$_4$ in the doping range $0.00 \le x=p
\le 0.30$ and Tl$_2$Ba$_2$CuO$_{6+\delta}$ at $p=0.20$ and $p=0.24$. The main
emphasis is placed on the response of electronic excitations in the
antiferromagnetic phase, in the pseudogap range, in the superconducting state,
and in the essentially normal metallic state at $x \ge 0.26$, where no
superconductivity could be observed. In most of the cases we compare B$_{1g}$
and B$_{2g}$ spectra which project out electronic properties close to $(\pi,0)$
and $(\pi/2, \pi/2)$, respectively. In the channel of electron-hole excitations
we find universal behavior in B$_{2g}$ symmetry as long as the material
exhibits superconductivity at low temperature. In contrast, there is a strong
doping dependence in B$_{1g}$ symmetry: (i) In the doping range $0.20 \le p \le
0.25$ we observe rapid changes of shape and temperature dependence of the
spectra. (ii) In La$_{2-x}$Sr$_{x}$CuO$_4$ new structures appear for $x < 0.13$
which are superposed on the electron-hole continuum. The temperature dependence
as well as model calculations support an interpretation in terms of
charge-ordering fluctuations. For $x \le 0.05$ the response from fluctuations
disappears at B$_{1g}$ and appears at B$_{2g}$ symmetry in full agreement with
the orientation change of stripes found by neutron scattering. While, with a
grain of salt, the particle-hole continuum is universal for all cuprates the
response from fluctuating charge order in the range $0.05 \le p < 0.16$ is so
far found only in La$_{2-x}$Sr$_{x}$CuO$_4$. We conclude that
La$_{2-x}$Sr$_{x}$CuO$_4$ is close to static charge order and, for this reason,
may have a suppressed $T_c$.
