\begin{table}
\caption{ Mean error (uncertainty) of our flux determinations
for continuum, H$\alpha$, H$\beta$, H$\gamma$, and HeII$~4686$
emission lines in different years, and in the whole (11 years)
observation period. Columns: 
2 and 3 --  the estimated mean continuum flux error in
\% and its sigma;
4 and 5 --  the estimated mean H$\alpha$ flux
error in \% and its sigma; 6 and 7 -- the estimated mean
H$\beta$ flux error in \% and its sigma; 8 and 9 --  the estimated mean
H$\gamma$ flux error in \% and its sigma; 10  and 11 --  the
estimated mean  flux error in \% and its sigma, Bottom -- mean error (uncertainty)
in the whole (11 years) observation period.} \label{tab8} %\centering
\par
\begin{tabular}{lllllllllll}
\hline  \hline\noalign{\smallskip}
 Year   &$\varepsilon_{\rm c}$&$\pm$$\sigma$&$\varepsilon_{\rm H\alpha}$&$\pm$$\sigma$
 &$\varepsilon_{\rm H\beta}$&$\pm$$\sigma$ &$\varepsilon_{\rm H\gamma}$&$\pm$$\sigma$
 &$\varepsilon_{\rm HeII}$&$\pm$$\sigma$\\
\noalign{\smallskip}\hline
 1996  &3.9   &2.27  &1.9   &1.2   &3.90  &1.56  &7.5   &      &10.4   &4.20\\
 1997  &5.17  &2.98  &2.19  &1.63  &1.63  &1.81  &6.0   &1.62  &10.22  &4.20\\
 1998  &2.18  &1.37  &3.1   &2.4   &1.90  &1.42  &5.75  &1.62  &10.18  &4.70\\
 1999  &3.24  &2.22  &1.75  &1.28  &2.29  &1.68  &5.65  &4.95  & 6.26  &3.00\\
 2000  &2.3   &3.65  &3.62  &2.31  &2.12  &0.82  &2.88  &2.53  & 4.65  &4.47\\
 2001  &3.77  &3.16  &2.9   &1.13  &1.63  &2.25  &4.2   &1.7   &12.90  &4.67\\
 2002  &2.05  &1.38  &2.7   &1.66  &3.91  &2.44  &5.37  &5.9   & 5.60  &1.56\\
 2003  &3.34  &2.37  &2.8   &1.49  &2.86  &2.44  &4.82  &2.67  & 7.62  &4.76\\
 2004  &2.65  &2.26  &2.6   &0.8   &2.25  &3.18  &3.85  &4.45  & 7.28  &4.57\\
 2005  &2.37  &2.14  &2.72  &2.63  &1.96  &2.22  &3.3   &1.31  & 7.37  &5.86\\
 2006  &2.42  &1.76  &2.12  &1.68  &1.62  &1.34  &6.58  &1.97  & 8.62  &4.71\\
\hline
 mean  &2.84  &1.23  &2.46  &0.75  &2.37  &0.84  &4.99  &1.46   &7.78  &2.51\\
(1996--2006)&&&&&&&&&&                                                        \\
\hline
\end{tabular}
\end{table}