\crThis is an error you may encounter in LaTeX when a tabular
environment is being processed. "Alignment tabs" are the
& signs that separate the columns of a tabular; so the error
message
could arise from a simple typo, such as:! Extra alignment tab has been changed to \cr
\begin{tabular}{ll}
hello & there & jim \\
goodbye & now
\end{tabular}
where the second & in the first line of the table is more than the
two-column ll column specification can cope with - an extra
"l" in that solves the problem. (As a result of the error,
"jim" will be moved to a row of his own.)
Rather more difficult to spot is the occurrence of the error when
you're using alignment instructions in a "p" column:
\usepackage{array}
...
\begin{tabular}{l>{\raggedright}p{2in}}
here & we are again \\
happy & as can be
\end{tabular}
the problem here (as explained in
tabular cell alignment) is that the
\raggedright command in the column specification has overwritten
tabular's definition of \\, so that
"happy" appears in a new line of the second column, and the
following & appears to LaTeX just like the second
& in the first example above.
Get rid of the error in the way described in
tabular cell alignment - either use
\tabularnewline explicitly, or use the \RBS trick described
there.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=altabcr