diff --git a/main/admin/event_type.php b/main/admin/event_type.php
index 913e6510d2..05ef25e620 100755
--- a/main/admin/event_type.php
+++ b/main/admin/event_type.php
@@ -319,7 +319,7 @@ echo Display::actions($action_array);
 
     <div class="col-md-4">
         <h4><?php echo get_lang('Users'); ?></h4>
-        <select multiple="1" id="usersList" class="span3 registration_case"></select>
+        <select multiple="1" id="usersList" class="registration_case"></select>
     </div>
     <div class="col-md-4">
         <div class="registration_case">
diff --git a/main/admin/settings.lib.php b/main/admin/settings.lib.php
index 52efadebce..b990cd3d5f 100755
--- a/main/admin/settings.lib.php
+++ b/main/admin/settings.lib.php
@@ -1276,7 +1276,7 @@ function generate_settings_form($settings, $settings_by_access_list)
                 } elseif ($row['variable'] == 'platform_charset') {
                     continue;
                 } else {
-                    $hideme['class'] = 'span4';
+                    $hideme['class'] = 'col-md-4';
                     $form->addElement(
                         'text',
                         $row['variable'],
diff --git a/main/auth/gotocourse.php b/main/auth/gotocourse.php
index 3b9c268bb4..ef5a8ee0e8 100755
--- a/main/auth/gotocourse.php
+++ b/main/auth/gotocourse.php
@@ -27,8 +27,8 @@ if (isset($_GET['firstpage'])) {
     $action = api_get_self().'?'.Security::remove_XSS($_SERVER['QUERY_STRING']);
     $action = str_replace('&amp;', '&', $action);
     $form = new FormValidator('formLogin', 'post', $action, null, array('class'=>'form-stacked'));
-    $form->addElement('text', 'login', null, array('placeholder' => get_lang('UserName'), 'class' => 'span3 autocapitalize_off')); //new
-    $form->addElement('password', 'password', null, array('placeholder' => get_lang('Password'), 'class' => 'span3')); //new
+    $form->addElement('text', 'login', null, array('placeholder' => get_lang('UserName'), 'class' => 'autocapitalize_off')); //new
+    $form->addElement('password', 'password', null, array('placeholder' => get_lang('Password'))); //new
     $form->addButtonNext(get_lang('LoginEnter'), 'submitAuth');
     // see same text in main_api.lib.php function api_not_allowed
     if (api_is_cas_activated()) {
diff --git a/main/document/slideshow.php b/main/document/slideshow.php
index 16c64c8dd6..d16ca9377d 100755
--- a/main/document/slideshow.php
+++ b/main/document/slideshow.php
@@ -330,7 +330,7 @@ if ($slide_id == 'all') {
 	for ($k = 0; $k < $number_iteration; $k++) {
 		for ($i = 0; $i < $number_image; $i++) {
 			if (isset($image_tag[$p])) {
-				echo '<li class="span4">
+				echo '<li class="col-md-4">
                       <div class="thumbnail">';
 				echo '<a href="slideshow.php?slide_id='.$p.'&curdirpath='.$pathurl.'">'.$image_tag[$p].'</a>';
 				echo '</div>';
diff --git a/main/exercice/calculated_answer.class.php b/main/exercice/calculated_answer.class.php
index d644e09ffc..05b6b1ec9a 100644
--- a/main/exercice/calculated_answer.class.php
+++ b/main/exercice/calculated_answer.class.php
@@ -152,13 +152,13 @@ class CalculatedAnswer extends Question
 
         $form->addElement('label', null, get_lang('FormulaExample'));
 
-        $form->addElement('text', 'formula', get_lang('Formula'), array('id' => 'formula', 'class' => 'span4'));
+        $form->addElement('text', 'formula', get_lang('Formula'), array('id' => 'formula'));
         $form->addRule('formula', get_lang('GiveFormula'), 'required');
 
-        $form->addElement('text', 'weighting', get_lang('Weighting'), array('id' => 'weighting', 'class' => 'span1'));
+        $form->addElement('text', 'weighting', get_lang('Weighting'), array('id' => 'weighting'));
         $form->setDefaults(array('weighting' => '10'));
 
-        $form->addElement('text', 'answerVariations', get_lang('AnswerVariations'), array('class' => 'span1'));
+        $form->addElement('text', 'answerVariations', get_lang('AnswerVariations'));
         $form->addRule('answerVariations', get_lang('GiveAnswerVariations'),'required');
         $form->setDefaults(array('answerVariations' => '1'));
 
diff --git a/main/gradebook/lib/fe/catform.class.php b/main/gradebook/lib/fe/catform.class.php
index c426029a88..90280b409e 100755
--- a/main/gradebook/lib/fe/catform.class.php
+++ b/main/gradebook/lib/fe/catform.class.php
@@ -199,7 +199,7 @@ class CatForm extends FormValidator
             'name',
             get_lang('CategoryName'),
             true,
-            array('class' => 'span3', 'maxlength' => '50')
+            array('maxlength' => '50')
         );
         $this->addRule('name', get_lang('ThisFieldIsRequired'), 'required');
 
diff --git a/main/gradebook/lib/fe/evalform.class.php b/main/gradebook/lib/fe/evalform.class.php
index ceede874f8..11a64502a3 100755
--- a/main/gradebook/lib/fe/evalform.class.php
+++ b/main/gradebook/lib/fe/evalform.class.php
@@ -277,7 +277,7 @@ class EvalForm extends FormValidator
 
             $element_name = 'score[' . $user[0] . ']';
 
-            $scoreColumnProperties = array('class' => 'span1', 'maxlength' => 5);
+            $scoreColumnProperties = array('maxlength' => 5);
             if ($firstUser) {
                 $scoreColumnProperties['autofocus'] = '';
                 $firstUser = false;
@@ -430,7 +430,6 @@ class EvalForm extends FormValidator
         $this->addElement('hidden', 'hid_course_code');
 
         $this->addText('name', get_lang('EvaluationName'), true, array(
-            'class' => 'span3',
             'maxlength' => '50',
             'id' => 'evaluation_title'
         ));
diff --git a/main/inc/lib/AnnouncementManager.php b/main/inc/lib/AnnouncementManager.php
index a01a360b1f..20f295bc27 100755
--- a/main/inc/lib/AnnouncementManager.php
+++ b/main/inc/lib/AnnouncementManager.php
@@ -861,7 +861,7 @@ class AnnouncementManager
         $userList = array(),
         $to_already_selected = array()
     ) {
-        echo '<select id="not_selected_form" name="not_selected_form[]" size="7" class="span4" multiple>';
+        echo '<select id="not_selected_form" name="not_selected_form[]" size="7" class="form-control" multiple>';
         // adding the groups to the select form
         if (!empty($groupList)) {
             foreach ($groupList as $this_group) {
@@ -920,7 +920,7 @@ class AnnouncementManager
         $ref_array_users = self::get_course_users();
 
         // we construct the form of the already selected groups / users
-        echo '<select id="selectedform" name="selectedform[]" size="7" multiple class="span4">';
+        echo '<select id="selectedform" name="selectedform[]" size="7" multiple class="form-control">';
         if (is_array($to_already_selected)) {
             foreach ($to_already_selected as $groupuser) {
                 list($type, $id) = explode(":", $groupuser);
diff --git a/main/inc/lib/grade_model.lib.php b/main/inc/lib/grade_model.lib.php
index cb37a09d27..df1728ef36 100755
--- a/main/inc/lib/grade_model.lib.php
+++ b/main/inc/lib/grade_model.lib.php
@@ -122,10 +122,10 @@ class GradeModel extends Model
 
         for ($i = 0; $i <= $max; $i++) {
             $counter = $i;
-            $form->addElement('text', 'components['.$i.'][percentage]', null, array('class' => 'span1'));
-            $form->addElement('text', 'components['.$i.'][acronym]',    null, array('class' => 'span1'));
-            $form->addElement('text', 'components['.$i.'][title]',      null, array('class' => 'span3'));
-            $form->addElement('hidden', 'components['.$i.'][id]',       null, array('class' => 'span3'));
+            $form->addElement('text', 'components['.$i.'][percentage]', null);
+            $form->addElement('text', 'components['.$i.'][acronym]',    null);
+            $form->addElement('text', 'components['.$i.'][title]',      null);
+            $form->addElement('hidden', 'components['.$i.'][id]',       null);
 
              $template_percentage =
             '<div id=' . $i . ' style="display: '.(($i<=$nr_items)?'inline':'none').';" class="control-group">
diff --git a/main/inc/lib/timeline.lib.php b/main/inc/lib/timeline.lib.php
index e9ede139f4..00baa5bbb4 100755
--- a/main/inc/lib/timeline.lib.php
+++ b/main/inc/lib/timeline.lib.php
@@ -138,12 +138,12 @@ class Timeline extends Model
         $parent_id = isset($_GET['parent_id']) ? intval($_GET['parent_id']) : '';
         $form->addElement('hidden', 'parent_id', $parent_id);
         $form->addElement('hidden', 'id', $id);
-        $form->addElement('text', 'headline', get_lang('Name'), array('class' => 'span4'));
+        $form->addElement('text', 'headline', get_lang('Name'));
 
         //@todo fix this
         $form->addElement('text', 'start_date', get_lang('StartDate'), array('size' => '70'));
         $form->addElement('text', 'end_date', get_lang('EndDate'), array('size' => '70'));
-        $form->addElement('textarea', 'text', get_lang('TimelineItemText'), array('class' => 'span3'));
+        $form->addElement('textarea', 'text', get_lang('TimelineItemText'));
         $form->addElement('text', 'media', get_lang('TimelineItemMedia'), array('size' => '70'));
         $form->addElement('text', 'media_caption', get_lang('TimelineItemMediaCaption'), array('size' => '70'));
         $form->addElement('text', 'media_credit', get_lang('TimelineItemMediaCredit'), array('size' => '70'));
diff --git a/main/newscorm/lp_build.php b/main/newscorm/lp_build.php
index 412dd99fc4..1ca4bf5399 100755
--- a/main/newscorm/lp_build.php
+++ b/main/newscorm/lp_build.php
@@ -147,7 +147,7 @@ echo '</div>';
 
 
 function show_block($link, $title, $subtitle, $icon) {
-    $html = '<li class="span4">';
+    $html = '<li class="col-md-4">';
         $html .=  '<div class="thumbnail">';
         $html .=  '<a href="'.$link.'" title="'.$title.'">';
         $html .=  Display::return_icon($icon, $title, array(), ICON_SIZE_BIG);
diff --git a/main/survey/generate_link.php b/main/survey/generate_link.php
index 42c3eabbe7..a1cd99c9fa 100755
--- a/main/survey/generate_link.php
+++ b/main/survey/generate_link.php
@@ -37,10 +37,10 @@ $link = SurveyManager::generate_survey_link(
     api_get_group_id()
 );
 echo '<div class="row">';
-    echo '<div class="span12" style="text-align:center">';
+    echo '<div class="col-md-12">';
     echo Display::url(get_lang('GenerateSurveyAccessLink'), $link, array('class' => 'btn btn-primary btn-large'));
     echo '</div>';
-    echo '<div class="span12">';
+    echo '<div class="col-md-12">';
     echo get_lang('GenerateSurveyAccessLinkExplanation');
 
     echo '<pre>';
diff --git a/main/survey/survey.lib.php b/main/survey/survey.lib.php
index 76f408a1aa..9536d8bffc 100755
--- a/main/survey/survey.lib.php
+++ b/main/survey/survey.lib.php
@@ -2299,7 +2299,7 @@ class SurveyUtil
                     array_push($chartData, array('option' => $optionText, 'votes' => $votes));
                 }
                 $chartContainerId = 'chartContainer'.$question['question_id'];
-                echo '<div id="'.$chartContainerId.'" class="span12">';
+                echo '<div id="'.$chartContainerId.'" class="col-md-12">';
                 echo self::drawChart($chartData, false, $chartContainerId);
 
                 // displaying the table: headers
@@ -2446,7 +2446,7 @@ class SurveyUtil
                 );
             }
         }
-        echo '<div id="chartContainer" class="span12">';
+        echo '<div id="chartContainer" class="col-md-12">';
         echo self::drawChart($chartData, true);
         echo '</div>';
 
@@ -3517,7 +3517,7 @@ class SurveyUtil
                 }
             }
             $tableHtml .=  '</table>';
-            echo '<div id="chartContainer" class="span12">';
+            echo '<div id="chartContainer" class="col-md-12">';
             echo self::drawChart($chartData, true);
             echo '</div>';
             echo $tableHtml;
diff --git a/main/template/default/skill/skill_tree.tpl b/main/template/default/skill/skill_tree.tpl
index 46e26d8154..1fcf6e4f46 100755
--- a/main/template/default/skill/skill_tree.tpl
+++ b/main/template/default/skill/skill_tree.tpl
@@ -454,7 +454,7 @@ $(document).ready(function() {
             <div class="control-group">            
                 <label class="control-label" for="name">{{'Description'|get_lang}}</label>            
                 <div class="controls">
-                    <textarea name="description" id="description" class="span3" rows="7"></textarea>
+                    <textarea name="description" id="description" rows="7"></textarea>
                 </div>
             </div>  
         </fieldset>
diff --git a/main/work/work.lib.php b/main/work/work.lib.php
index 9128194c85..dcde73c5b8 100755
--- a/main/work/work.lib.php
+++ b/main/work/work.lib.php
@@ -3417,7 +3417,7 @@ function setWorkUploadForm($form, $uploadFormType = 0)
     $form->addElement('hidden', 'contains_file', 0, array('id'=>'contains_file_id'));
     $form->addElement('hidden', 'active', 1);
     $form->addElement('hidden', 'accepted', 1);
-    $form->addElement('text', 'title', get_lang('Title'), array('id' => 'file_upload', 'class' => 'span4'));
+    $form->addElement('text', 'title', get_lang('Title'), array('id' => 'file_upload'));
     $form->addRule('title', get_lang('ThisFieldIsRequired'), 'required');
 
     switch ($uploadFormType) {