I have a really long table and it is out of margin. I read other post about this issue but I still cannot figure it out:
\begin{table}[htbp]
\begin{center}
\begin{tabular}{|c|c|c|p{51pt}|c|p{54pt}|c|c|}
\hline
&
Atmosphere pressure P$_{0}$&
Wanted pressure inside(absolute) P'&
$\mathrm{\Delta p}$ \par &
Altitude&
g (m$^{2}$/s) \par &
S (m$^{2})$&
m (g) \\
\hline
Los Angeles&
101.2KPa&
180Kpa&
78.8Kpa&
70m&
9.83268&
1.26*10$^{-5}$&
100.98 \\
\hline
Lhasa (capital of Tibet)&
65.3KPa&
102Kpa&
36.7Kpa&
3650m&
9.82143&
1.26*10$^{-5}$&
47.08 \\
\hline
Mt Everest Base Camp&
46.3KPa&
102Kpa&
55.7Kpa&
5550m&
9.81558&
1.26*10$^{-5}$&
71.50 \\
\hline
\end{tabular}
\label{tab3}
\end{center}
\end{table}

\documentclass{...}and ending with\end{document}. That may seem tedious to you, but think of the extra work it represents for TeX.SX users willing to help you. Help them help you: remove that one hurdle between you and a solution to your problem. – Mensch Oct 28 '13 at 16:05