--- system.module?rev=1.202	2005-03-25 23:48:35.000000000 +0100
+++ system.module	2005-03-28 00:46:01.000000000 +0200
@@ -117,6 +117,7 @@ function system_menu($may_cache) {
  * Menu callback: dummy clean URL tester.
  */
 function system_test() {
+  variable_set('clean_url_ok', 1);
 }
 
 /**
@@ -203,10 +204,11 @@ function system_view_general() {
   $group .= form_textfield(t('Anonymous user'), 'anonymous', variable_get('anonymous', 'Anonymous'), 70, 70, t('The name used to indicate anonymous users.'));
   $group .= form_textfield(t('Default front page'), 'site_frontpage', variable_get('site_frontpage', 'node'), 70, 70, t('The home page displays content from this relative URL.  If you are not using clean URLs, specify the part after "?q=".  If unsure, specify "node".'));
 
-  // check if clean URLs are supported (HTTP 200 = Ok)
-  $request = drupal_http_request($GLOBALS['base_url'] . '/system/test');
-  $supported = $request->code == 200;
-  $group .= form_radios(t('Clean URLs'), 'clean_url', variable_get('clean_url', 0), array(t('Disabled'), t('Enabled')), t('This option makes Drupal emit clean URLs (i.e. without <code>?q=</code> in the URL). You\'ll need <code>ModRewrite</code> support for this to work. See the <code>.htaccess</code> file in Drupal\'s top-level directory for more information.'), false, $supported ? NULL : array('disabled' => 'disabled'));
+  $group .= form_radios(t('Clean URLs'), 'clean_url', variable_get('clean_url', 0), array(t('Disabled'), t('Enabled')), t('This option makes Drupal emit clean URLs (i.e. without <code>?q=</code> in the URL). You\'ll need <code>ModRewrite</code> support for this to work. See the <code>.htaccess</code> file in Drupal\'s top-level directory for more information.'));
+  variable_set('clean_url_ok', 0);
+  global $base_url;
+  // We will use a random URL so there is no way a proxy or a browser could cache the "no such image" answer.
+  $group .= '<img style="margin-left: -1000em" src="'. $base_url. '/system/test/'. user_password(20) .'.png">';
 
   $output = form_group(t('General settings'), $group);
 
@@ -547,6 +549,10 @@ function system_settings_save() {
   }
   else if ($op == t('Save configuration')) {
     if (is_array($edit)) {
+      if ($edit['clean_url'] && !variable_get('clean_url_ok', 0)) {
+        drupal_set_message(t('Clean URL testing failed. Please recheck <code>ModRewrite</code> support.'), 'error');
+        $edit['clean_url'] = 0;
+      }
       foreach ($edit as $name => $value) {
         variable_set($name, $value);
       }