diff --git a/main/admin/languages.php b/main/admin/languages.php
index be9518cf85..78a79e5cb9 100755
--- a/main/admin/languages.php
+++ b/main/admin/languages.php
@@ -111,7 +111,7 @@ $htmlHeadXtra[] = '<script>
                 var action = datos.split(":")[0];
                 if (action && action == "confirm") {
                     var id = datos.split(":")[1];
-                    var sure = "<div class=\"warning-message\">'.get_lang('ThereAreUsersUsingThisLanguageYouWantToDisableThisLanguageAndSetUsersWithTheDefaultPortalLanguage').'</div><a href=\"languages.php?action=make_unavailable_confirmed&id="+id+"\" class=\"btn\">' . get_lang('MakeUnavailable') . '</a>";
+                    var sure = "<div class=\"warning-message\">'.get_lang('ThereAreUsersUsingThisLanguageYouWantToDisableThisLanguageAndSetUsersWithTheDefaultPortalLanguage').'</div><a href=\"languages.php?action=make_unavailable_confirmed&id="+id+"\" class=\"btn btn-default\">' . get_lang('MakeUnavailable') . '</a>";
                     $("#id_content_message").html(sure);
 				}
 		} });
diff --git a/main/coursecopy/classes/CourseSelectForm.class.php b/main/coursecopy/classes/CourseSelectForm.class.php
index 92a291486e..60c9230851 100755
--- a/main/coursecopy/classes/CourseSelectForm.class.php
+++ b/main/coursecopy/classes/CourseSelectForm.class.php
@@ -217,8 +217,8 @@ class CourseSelectForm
 
 						echo '<blockquote>';
                         echo '<div class="btn-group">';
-						echo "<a class=\"btn\" href=\"javascript: void(0);\" onclick=\"javascript: setCheckbox('$type',true);\" >".get_lang('All')."</a>";
-                        echo "<a class=\"btn\" href=\"javascript: void(0);\" onclick=\"javascript:setCheckbox('$type',false);\" >".get_lang('None')."</a>";
+						echo "<a class=\"btn btn-default\" href=\"javascript: void(0);\" onclick=\"javascript: setCheckbox('$type',true);\" >".get_lang('All')."</a>";
+                        echo "<a class=\"btn btn-default\" href=\"javascript: void(0);\" onclick=\"javascript:setCheckbox('$type',false);\" >".get_lang('None')."</a>";
 						echo '</div><br />';
 
 						foreach ($resources as $id => $resource) {
diff --git a/main/coursecopy/import_backup.php b/main/coursecopy/import_backup.php
index 4886a4efef..fc1db22193 100755
--- a/main/coursecopy/import_backup.php
+++ b/main/coursecopy/import_backup.php
@@ -96,21 +96,21 @@ if (Security::check_token('post') && (
         $cr->set_file_option($_POST['same_file_name_option']);
         $cr->restore();
         Display::display_normal_message(get_lang('ImportFinished'));
-        echo '<a class="btn" href="' . api_get_path(WEB_COURSE_PATH) . api_get_course_path() . '/index.php">' . get_lang('CourseHomepage') . '</a>';
+        echo '<a class="btn btn-default" href="' . api_get_path(WEB_COURSE_PATH) . api_get_course_path() . '/index.php">' . get_lang('CourseHomepage') . '</a>';
     } else {
         if (!$error) {
             Display::display_warning_message(get_lang('NoResourcesInBackupFile'));
-            echo '<a class="btn" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
+            echo '<a class="btn btn-default" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
         } elseif ($filename === false) {
             Display::display_error_message(get_lang('ArchivesDirectoryNotWriteableContactAdmin'));
-            echo '<a class="btn" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
+            echo '<a class="btn btn-default" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
         } else {
             if ($filename == '') {
                 Display::display_error_message(get_lang('SelectBackupFile'));
-                echo '<a class="btn" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
+                echo '<a class="btn btn-default" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
             } else {
                 Display::display_error_message(get_lang('UploadError'));
-                echo '<a class="btn" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
+                echo '<a class="btn btn-default" href="import_backup.php?' . api_get_cidreq() . '">' . get_lang('TryAgain') . '</a>';
             }
         }
     }
diff --git a/main/create_course/add_course.php b/main/create_course/add_course.php
index 3445eab190..fc8dd618f1 100755
--- a/main/create_course/add_course.php
+++ b/main/create_course/add_course.php
@@ -245,7 +245,7 @@ if ($form->validate()) {
                 $message = (is_array($course_request_info) ? '<strong>'.$course_request_info['code'].'</strong> : ' : '').get_lang('CourseRequestCreated');
                 $message = Display :: return_message($message, 'confirmation', false);
                 $message .=  '<div style="float: left; margin:0px; padding: 0px;">' .
-                    '<a class="btn" href="'.api_get_path(WEB_PATH).'user_portal.php">'.get_lang('Enter').'</a>' .
+                    '<a class="btn btn-default" href="'.api_get_path(WEB_PATH).'user_portal.php">'.get_lang('Enter').'</a>' .
                     '</div>';
             } else {
                 $message = Display :: return_message(get_lang('CourseRequestCreationFailed'), 'error', false);
diff --git a/main/dropbox/recover_dropbox_files.php b/main/dropbox/recover_dropbox_files.php
index 6e7bdf27a7..c7e78bc81e 100755
--- a/main/dropbox/recover_dropbox_files.php
+++ b/main/dropbox/recover_dropbox_files.php
@@ -42,7 +42,7 @@ if (Database::num_rows($result)) {
             $rows[] = array(
                     $file['filename'],
                     api_convert_and_format_date($file['upload_date']),
-                    Display::url(get_lang('Recover'), api_get_self().'?recover_id='.$file['id'], array('class' => 'btn'))
+                    Display::url(get_lang('Recover'), api_get_self().'?recover_id='.$file['id'], array('class' => 'btn btn-default'))
             );
         }
     }
diff --git a/main/exercice/answer_admin.inc.php b/main/exercice/answer_admin.inc.php
index f85aee7087..a97bf266bb 100755
--- a/main/exercice/answer_admin.inc.php
+++ b/main/exercice/answer_admin.inc.php
@@ -1150,8 +1150,8 @@ if ($modifyAnswers) {
 
                         <tr>
                             <td colspan="4">
-                                <button type="submit" class="btn minus" name="lessMatches" value="<?php echo get_lang('LessElements'); ?>"><?php echo get_lang('LessElements'); ?></button>
-                                &nbsp;&nbsp;<button class="btn plus" type="submit" name="moreMatches" value="<?php echo get_lang('MoreElements'); ?>"><?php echo get_lang('MoreElements'); ?></button>
+                                <button type="submit" class="btn btn-danger" name="lessMatches" value="<?php echo get_lang('LessElements'); ?>"><?php echo get_lang('LessElements'); ?></button>
+                                &nbsp;&nbsp;<button class="btn btn-success" type="submit" name="moreMatches" value="<?php echo get_lang('MoreElements'); ?>"><?php echo get_lang('MoreElements'); ?></button>
                             </td>
                         </tr>
                         <tr>
diff --git a/main/inc/ajax/user_manager.ajax.php b/main/inc/ajax/user_manager.ajax.php
index 7bdb33a23c..9c62065e74 100755
--- a/main/inc/ajax/user_manager.ajax.php
+++ b/main/inc/ajax/user_manager.ajax.php
@@ -25,7 +25,7 @@ switch ($action) {
                 $user_info['mail'] = ' '.$user_info['mail'].' ';
             }
             echo '<h3>'.$user_info['complete_name'].'</h3>'.$user_info['mail'].$user_info['official_code'];
-            echo '<br/><br/><a class="btn" href="'.api_get_path(WEB_CODE_PATH).'social/profile.php?u='.$user_info['user_id'].'">'.get_lang('ViewSharedProfile').'</a>';
+            echo '<br/><br/><a class="btn btn-default" href="'.api_get_path(WEB_CODE_PATH).'social/profile.php?u='.$user_info['user_id'].'">'.get_lang('ViewSharedProfile').'</a>';
             echo '</div>';
             echo '</div>';
         echo '</div>';