warnings
What LaTeX is trying to do with this:
\documentclass{article}
\usepackage{floatflt}
\begin{document}
\begin{floatingtable}[r]{
\begin{tabular}{cc}
0 & 1 \\
1 & 0
\end{tabular}}
\end{floatingtable}
This is MWE.
\end{document}
I got
Underfull \hbox (badness 10000) in paragraph at lines 9--10
and message disappears if I add \raggedright after \begin{document}. It does not make any difference if I add more words to "This is MWE." -paragraph or add few paragraphs more.
Inserting \par\vspace{\baselineskip} would provide you with a single line gap between two paragraphs. In the following minimal example, a mock-up of a solution environment adds \par\nobreak\vspace{\baselineskip} after every \begin{solution}{<stuff>} (the \nobreak addition discourages page breaking after printing the environment header). If you don't want it this way, you can add the gap manually by removing \par\vspace{\baselineskip} from the definition of \begin{solution}:
\documentclass{article}
\usepackage{array}% http://ctan.org/pkg/array
\newenvironment{solution}[1] % solution environment
{\par\textbf{Solution\ #1}:\par\nobreak\vspace{\baselineskip}}% \begin{solution}
{}% \end{solution}
\begin{document}
\begin{solution}{1.2} % Line 107
\newlength{\mylen}\settowidth{\mylen}{$p \to q$}% Widest element
\begin{tabular}{*{5}{|>{\centering\arraybackslash\rule{0pt}{1.05em}}m{\mylen}}|}
\hline
$p$ & $q$ & $p \land q$ & $p \lor q$ & $p \to q$\\
\hline
T & T & T & T & T \\
\hline
T & F & F & T & F \\
\hline
F & T & F & T & T \\
\hline
F & F & F & F & T \\
\hline
\end{tabular}
\end{solution}
\end{document}
You might also consider using \smallskip, \medskip or \bigskip, each of which allows for some stretching/shrinking within the text.
The lines of the first cell of the second line doesn't fill the hbox-es (3 bad boxes). Same at the third cell for one line (1 bad box). Using \raggedright can make these bad boxes go away without the real change of output. This is because the box is small but the words are long: you can't really use justification when you have 1 word per line. (If you have a few words per line, you can try \sloppy.)
The last bad box is caused by the fact that your tabular is larger than the actual \hsize. That's because it is wider than the sum of the column widths. Using the showframe package, you can clearly see that in the example below (\raggedright already added, 1 bad box remaining). You can fix this by resizing a column or changing the column separation (or check this topic).
\documentclass{article}
\usepackage{showframe}
\begin{document}
\begin{table}[!ht]
\caption{Comparison of design requirements for adults and children}
\footnotesize
\begin{center}
\begin{tabular}{|p{0.2\textwidth}|p{0.35\textwidth}|p{0.35\textwidth}|}
\hline \centering{Message} & \centering{Adults} & \centering{Children} \tabularnewline
\hline \raggedright*M1-constraint-requirement-requirement-summary & \raggedright``The target user is an \textbf{adult}. Constraints - Ergonomics can be found in standard \textbf{XX1}.''& \raggedright``The target user is a \textbf{child}. Constraints - Ergonomics can be found in standard \textbf{XX2}.'' \tabularnewline
\hline
\end{tabular}
\end{center}
\end{table}
\end{document}
Best Answer
There is no warning if
\centeringis issued before\begin{tabular}: