remove Drupal module and core default CSS

template.php

<?php
function theme_preprocess_page(&$vars) {
  //remove drupal default system CSS (IE can only take 31 CSS files)
  $css = drupal_add_css();
  $rm_css = array(
    'modules/node/node.css',
    'modules/poll/poll.css',
    'modules/system/defaults.css',
    //'modules/system/system.css',
    //'modules/system/system-menus.css',
    'modules/user/user.css',
    //'sites/all/modules/contrib/admin_menu/admin_menu.css',
    //'sites/all/modules/contrib/cck/theme/content-module.css',
    //'sites/all/modules/contrib/ckeditor/ckeditor.css',
    'sites/all/modules/contrib/ctools/css/ctools.css',
    'sites/all/modules/contrib/date/date.css',
    'sites/all/modules/contrib/date/date_popup/themes/datepicker.css',
    'sites/all/modules/contrib/date/date_popup/themes/jquery.timeentry.css',
    //'sites/all/modules/contrib/filefield/filefield.css',
    'sites/all/modules/contrib/logintoboggan/logintoboggan.css',
    'sites/all/modules/contrib/tweetmeme/tweetmeme.css',
    //'sites/all/modules/contrib/admin/includes/admin.toolbar.base.css',
    //'sites/all/modules/contrib/admin/includes/admin.toolbar.css',
    //'sites/all/modules/contrib/admin/includes/admin.menu.css',
    //'sites/all/modules/contrib/cck/modules/fieldgroup/fieldgroup.css',
    //'sites/all/modules/contrib/views/css/views.css',
    //'sites/all/modules/contrib/context/context_layouts/plugins/context_layouts_reaction_block.css',
    //'sites/all/modules/contrib/context/plugins/context_reaction_block.css',
    //'sites/all/modules/contrib/context/context_ui/context_ui.css',
    //'sites/all/modules/contrib/viewsdisplaytabs/viewsdisplaytabs.css',
  );
  foreach ($rm_css as $key => $value) {
    unset($css['all']['module'][$value]);
  }
  $vars['styles'] = drupal_get_css($css);
}