I need some table in LaTeX. As you can see, my LaTeX code is following

\setlength{\extrarowheight}{7.6pt}
\begin{footnotesize}
\begin{tabular}{l|m{7cm}}
\hline
\hline
\hline
\hline
mix-1 & mcf, libquantum, \\
\hline
mix-2 & sphinx3, soplex, \\
\hline
mix-3 & omnetpp, xalancbmk, \\
\hline
\hline
\end{tabular}
\end{footnotesize}


Actually, I could not understand array packages. I meant it's m{2.5cm}'s use method. I want to align a text in right side into vertical center like left side.

Can you help me? Some explain in other site make me confused because I'm not expert in LaTeX.

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Welcome to TeX.SE. Your table seems to work fine if you comment out the setlength{\extrarowheight}{7.6pt} and include \usepackage{array} in the preamble.  –  Peter Grill Nov 16 '11 at 5:45
use \footnotesize as a switch and not as an environment –  Herbert Nov 16 '11 at 8:47

In terms of vertically centering the content in your tabular cells, you don't need to set \extrarowheight. However, using m{<len>} (where <len> is any recognized TeX length) becomes useful when your right-hand column has a little more substance to it (that is, it is longer).

If you're interested in more vertical padding around the entries, modify \arraystretch instead. It provides a factor with which the rows are stretched/expanded:

\documentclass{article}
\usepackage{array}% http://ctan.org/pkg/array
\begin{document}
\renewcommand{\arraystretch}{2.5}% array stretch factor
\begin{footnotesize}
\begin{tabular}{l|p{7cm}}
\hline
\hline
\hline
\hline
mix-1 & mcf, libquantum, \\
\hline
mix-2 & sphinx3, soplex, \\
\hline
mix-3 & omnetpp, xalancbmk, \\
\hline
\hline
\end{tabular}
\end{footnotesize}
\end{document}


For more information on padding of cell entries with a tabular (both horizontally and vertically), see Column padding in tables.

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I think your issue is your premable. If you include \usepackage{array} this compiles. Also, you should move the \setlength{\extrarowheight}{7.6pt} to be within a group (unless you want this to apply to all tables), you get:

\documentclass{article}
\usepackage{array}
\begin{document}
\begin{footnotesize} \setlength{\extrarowheight}{7.6pt}
\begin{tabular}{l|m{7cm}}
\hline
\hline
\hline
\hline
mix-1 & mcf, libquantum, \\
\hline
mix-2 & sphinx3, soplex, \\
\hline
mix-3 & omnetpp, xalancbmk, \\
\hline
\hline
\end{tabular}
\end{footnotesize}
\end{document}


If you want both columns to be vertically centered then you have to use

\begin{tabular}{m{1.5cm}|m{7cm}}


which yields the following. The extra vertical space above the data is coming from your setting of \extrarowheight`.

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