In the "Advanced summary" page, the graphs are not centered (even if the align property in the TD tag is set to center).

Fix: Use class instead of align:
for ( $t_pos = 0; $t_pos < count($t_graphs ); $t_pos++ ) {
if ( 0 == ( $t_pos % $t_wide ) ) {
print( "<tr valign=\"top\">\n" );
}
echo '<td width="50%" class="center">';
printf("<img src=\"%s.php?width=%d\" border=\"0\" />", $t_graphs[$t_pos], $t_graph_width );
echo '</td>';
if ( ( $t_wide - 1 ) == ( $t_pos % $t_wide ) ) {
print( "</tr>\n" );
}
}