tabulary: overflow and column squeezing

Question

I am having problems with tabulary in a 2-column table. If column2 has multiple lines of text, it causes column1 to be squeezed to a ridiculously small width. And column1 sometimes overflows into column2. Basic markup:

 \usepackage{tabulary}
    ...
    begin{table}[H]
begin{tabulary}{.9\textwidth}[]{|L|L|}
...
\end{tabulary}
    \end{table}

More detail:

    {\small\begin{table}[H]
\caption{Conventions Used in This Document}
\begin{tabulary}{.9\textwidth}[]{|L|L|}
\hline
\textbf{Convention}
 & \textbf{
                            Meaning
                        }

\\ \hline



                            \textbf{boldface}
                         & 

Boldface type indicates graphical user interface elements associated with an action, or terms
                            defined in text or the glossary.
\\ \hline



                            \textit{italic}
                         & 

 Italic type indicates book titles, emphasis, or placeholder variables for which you supply
                            particular values. 
\\ \hline



                            \texttt{monospace}
                         & 

 Monospace type indicates commands within a paragraph, URLs, code in examples, text that
                            appears on the screen, or text that you enter. 
\\ \hline

\end{tabulary}
\end{table}

Suggested fix of replacing {|L|L|} with {|1L|} fails with following error:

! Package array Error:  Illegal pream-token (1): `c' used.

Answer 1

No usable example is provided so this is untested but as there should be no linebreaking in the first column it should be a standard l column not an L column which is a parbox column like >\raggedright}p{...} for some calculated width.

So use

\begin{tabulary}{\textwidth}{|l|L|}

Note using .9\textwidth forces the table to be off-centre with a strange 10% margin at the right hand side.