public function flush() {
        if (empty($this->_row) or empty($this->_row['line']['normal'])) {
            // Nothing to print - each line has to have at least number
            $this->_row = array();
            foreach ($this->columns as $col) {
                $this->_row[$col] = array('normal'=>'', 'info'=>'', 'warning'=>'', 'error'=>'');
            }
            return;
        }
        $ci = 0;
        $ri = 1;
        echo '<tr class="r'.$ri.'">';
        foreach ($this->_row as $key=>$field) {
            foreach ($field as $type=>$content) {
                if ($field[$type] !== '') {
                    $field[$type] = '<span class="uu'.$type.'">'.$field[$type].'</span>';
                } else {
                    unset($field[$type]);
                }
            }
            echo '<td class="cell c'.$ci++.'">';
            if (!empty($field)) {
                echo implode('<br />', $field);
            } else {
                echo '&nbsp;';
            }
            echo '</td>';
        }
        echo '</tr>';
        foreach ($this->columns as $col) {
            $this->_row[$col] = array('normal'=>'', 'info'=>'', 'warning'=>'', 'error'=>'');
        }
    }