I am using memoir template.
I have a small table (attached is the word version) and I tried to center it against the page. But it becomes left aligned after I added [H] behind \begin{table}.
Here is the link of the template and the code: https://sites.google.com/site/biometricbiometrie/template/monStyle.tex?attredirects=0&d=1

\definecolor{c1}{rgb}{0.30980, 0.50588, 0.73725}
\definecolor{c2}{rgb}{0.82353, 0.87843, 0.92941}
\begin{center}
\setlength{\arrayrulewidth}{1pt}
\setlength{\extrarowheight}{1.2pt}
\color{c1}
\arrayrulecolor{white}
\begin{table}[H]
\caption{Table}
\label{tb33}
\begin{tabular}{|l|l|c|}
\rowcolor{c1}
& \color{c2}F1A & \color{c2}F3A \\
\hline
\rowcolor{c2}
F2A & 0.4693 (14.2\%) & 0.5073 (15.3\%) \\
\hline
\rowcolor{c2}
F1A & & 0.4191 (12.6\%) \\
\hline
\end{tabular}
\end{table}
\end{center}