You want a float whose contents are centred, but LaTeX ignores your
center environment. Most likely, you have written:
\begin{center}
\begin{figure}
...
\end{figure}
\end{center}
In this case, LaTeX has “taken the figure away”,
and will typeset it at some location it fancies (it does the same with
tables) the only thing we can say (for sure) about the
location is that it won’t be inside that center
environment. As a result, the center environment is
left with nothing to do … except to
make a mess of your vertical spacing.
The solution is the same as that outlined in
the same answer, noting that all control of
an figure or table needs to be
inside the environment. So the example’s code should be converted to
\begin{figure}
\centering
...
\end{figure}
(or something similar for a table).
This answer last edited: 2013-11-19
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=centre-flt