However, I have got a problem, I can't solve it. I would like to make a table like belows, but cannot merge cell without loosing the arrangement:
\begin{table}[ht]
\centering
\setlength{\tabcolsep}{1pt}
\begin{tabular}{|p{1.8cm}|l|l|l|l|l|l|l|l|p{4.8cm}|p{4.5cm}|}
\hline
& \multicolumn{7}{|c|}{\textbf{Supported Devices}} & & & \\ \hline
\textbf{Site} & \begin{sideways}Mobile Site\end{sideways} &
\begin{sideways}Android\end{sideways} &
\begin{sideways}iPhone\end{sideways} &
\begin{sideways}Blackbery\end{sideways} &
\begin{sideways}Windows Mobile \end{sideways} &
\begin{sideways}Symbian\end{sideways} &
\begin{sideways}Palm\end{sideways} &
\begin{sideways}W3C Geo API\end{sideways} & \textbf{Significant features} &
\textbf{Notes}\\ \hline
\textbf{FourSquare} & x & x & x & x & x & x & & & Support games for differentiation & \\ \hline
\textbf{Facebook} & x & x & & & & & & x & High number of users & Not supported in Vietnam \\ \hline
\textbf{Latitude} & x & x & x & x & & & x & x & & \\ \hline
\textbf{Gowalla} & x & x & x & x & x & & & x & & \\ \hline
\textbf{Twitter} & x & x & x & x & x & & & x & & \\ \hline
\textbf{Yelp} & x & x & x & x & x & & x & & Focus on information searching & \\ \hline
\textbf{Loopt} & & x & x & x & x & & & & & \\ \hline
\textbf{GyPSii} & & x & x & x & x & x & & & & \\ \hline
\textbf{IYOUIT} & x & x & x & x & x & x & x & x & & \\ \hline
\textbf{Yoo! } & & & & & & & & & First social network supported location awareness in Vietnam & Not have mobile web version \\ \hline
\end{tabular}
\caption{social networks support location aware}\label{table1}
\end{table}
