views theme.inc arround line 500

theme.inc

<?php

function template_preprocess_views_view_unformatted(&$vars) {
  $view     = $vars['view'];
  $rows     = $vars['rows'];

  $vars['classes'] = array();
  // Set up striping values.
  foreach ($rows as $id => $row) {
    $row_classes = array();
    $row_classes[] = 'views-row';
    $row_classes[] = 'views-row-' . ($id + 1);
    $row_classes[] = 'views-row-' . ($id % 2 ? 'even' : 'odd');
    if ($id == 0) {
      $row_classes[] = 'views-row-first';
    }
    if ($id == count($rows) -1) {
      $row_classes[] = 'views-row-last';
    }
    // Flatten the classes to a string for each row for the template file.
    $vars['classes'][$id] = implode(' ', $row_classes);
  }
}