\documentclass{article}
% Tabular example from LaTeX manual, p.205
\begin{document}
\begin{tabular}{|r||r@{--}l|p{1.25in}|}
\hline
\multicolumn{4}{|c|}{GG\&A Hoofed Stock}
  \\ \hline\hline
&\multicolumn{2}{c|}{Price}& \\ \cline{2-3}
\multicolumn{1}{|c||}{Year}
& \multicolumn{1}{r@{\,\vline\,}}{low}
& high & \multicolumn{1}{c|}{Comments}
 \\ \hline
1971 &  97 & 245 & Bad year.\\ \hline
  72 & 245 & 245 & Light trading due to a heavy winter. \\ \hline
  73 & 245 & 2001 & No gnus was very good gnus this year. \\ \hline
\end{tabular}

\begin{tabular}{|c|c|c|}\hline
x&&x\\\hline
&&\\\hline
x&&x\\\hline
\end{tabular}

\begin{tabular}{ @{1} p{3em} @{2} p{3em} @{3} p{3em} @{4} }
a&b&c\\
a a a  a a a a a a a&b&c\\
\end{tabular}

\end{document}
