diff --git a/css/swad18.57.css b/css/swad18.60.1.css
similarity index 99%
rename from css/swad18.57.css
rename to css/swad18.60.1.css
index ad8f7292..8dd66994 100644
--- a/css/swad18.57.css
+++ b/css/swad18.60.1.css
@@ -2614,6 +2614,11 @@ a:hover img.CENTRE_PHOTO_SHOW
 .TT_TUTO	{box-sizing:border-box; height:16px; background-color:#D6E9C3; border:solid 2px; border-color:#E8FCD3 #C2D4B1 #C2D4B1 #E8FCD3;}
 
 /********************************* Preference ********************************/
+
+.PREF_CONTAINERS
+	{
+	margin:0 auto;
+	}
 .PREF_CONTAINER
 	{
 	display:inline-block;
diff --git a/swad_agenda.c b/swad_agenda.c
index 4d66a78c..da246c02 100644
--- a/swad_agenda.c
+++ b/swad_agenda.c
@@ -42,6 +42,7 @@
 #include "swad_pagination.h"
 #include "swad_parameter.h"
 #include "swad_photo.h"
+#include "swad_preference.h"
 #include "swad_privacy.h"
 #include "swad_QR.h"
 #include "swad_string.h"
@@ -157,9 +158,11 @@ void Agd_ShowMyAgenda (void)
 		 Hlp_PROFILE_Agenda,Box_NOT_CLOSABLE);
 
    /***** Put forms to choice which events to show *****/
+   Pre_StartPrefsHead ();
    Agd_ShowFormToSelPast__FutureEvents ();
    Agd_ShowFormToSelPrivatPublicEvents ();
    Agd_ShowFormToSelHiddenVisiblEvents ();
+   Pre_EndPrefsHead ();
 
    /***** Show the current events in the user's agenda *****/
    Agd_ShowEventsToday (Agd_MY_AGENDA_TODAY);
@@ -185,7 +188,7 @@ static void Agd_ShowFormToSelPast__FutureEvents (void)
       "calendar-plus.svg",	// Agd_FUTURE_EVENTS
      };
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (PstFut = Agd_PAST___EVENTS;
 	PstFut <= Agd_FUTURE_EVENTS;
 	PstFut++)
@@ -204,7 +207,7 @@ static void Agd_ShowFormToSelPast__FutureEvents (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
@@ -221,7 +224,7 @@ static void Agd_ShowFormToSelPrivatPublicEvents (void)
       "unlock.svg",	// Agd_PUBLIC_EVENTS
      };
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (PrvPub = Agd_PRIVAT_EVENTS;
 	PrvPub <= Agd_PUBLIC_EVENTS;
 	PrvPub++)
@@ -240,7 +243,7 @@ static void Agd_ShowFormToSelPrivatPublicEvents (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
@@ -257,7 +260,7 @@ static void Agd_ShowFormToSelHiddenVisiblEvents (void)
       "eye.svg",	// Agd_VISIBL_EVENTS
      };
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (HidVis = Agd_HIDDEN_EVENTS;
 	HidVis <= Agd_VISIBL_EVENTS;
 	HidVis++)
@@ -276,7 +279,7 @@ static void Agd_ShowFormToSelHiddenVisiblEvents (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
diff --git a/swad_assignment.c b/swad_assignment.c
index e6902d69..57e429f1 100644
--- a/swad_assignment.c
+++ b/swad_assignment.c
@@ -41,6 +41,7 @@
 #include "swad_pagination.h"
 #include "swad_parameter.h"
 #include "swad_photo.h"
+#include "swad_preference.h"
 #include "swad_string.h"
 #include "swad_table.h"
 
@@ -72,7 +73,6 @@ static bool Asg_CheckIfICanCreateAssignments (void);
 static void Asg_PutIconsListAssignments (void);
 static void Asg_PutIconToCreateNewAsg (void);
 static void Asg_PutButtonToCreateNewAsg (void);
-static void Asg_PutFormToSelectWhichGroupsToShow (void);
 static void Asg_ParamsWhichGroupsToShow (void);
 static void Asg_ShowOneAssignment (long AsgCod,bool PrintView);
 static void Asg_WriteAsgAuthor (struct Assignment *Asg);
@@ -146,7 +146,11 @@ static void Asg_ShowAllAssignments (void)
 
    /***** Select whether show only my groups or all groups *****/
    if (Gbl.CurrentCrs.Grps.NumGrps)
-      Asg_PutFormToSelectWhichGroupsToShow ();
+     {
+      Pre_StartPrefsHead ();
+      Grp_ShowFormToSelWhichGrps (ActSeeAsg,Asg_ParamsWhichGroupsToShow);
+      Pre_EndPrefsHead ();
+     }
 
    if (Gbl.Asgs.Num)
      {
@@ -291,16 +295,9 @@ static void Asg_PutButtonToCreateNewAsg (void)
   }
 
 /*****************************************************************************/
-/***************** Put form to select which groups to show *******************/
+/**************** Put params to select which groups to show ******************/
 /*****************************************************************************/
 
-static void Asg_PutFormToSelectWhichGroupsToShow (void)
-  {
-   fprintf (Gbl.F.Out,"<div style=\"display:table; margin:0 auto;\">");
-   Grp_ShowFormToSelWhichGrps (ActSeeAsg,Asg_ParamsWhichGroupsToShow);
-   fprintf (Gbl.F.Out,"</div>");
-  }
-
 static void Asg_ParamsWhichGroupsToShow (void)
   {
    Asg_PutHiddenParamAsgOrder ();
diff --git a/swad_attendance.c b/swad_attendance.c
index f9ed8c59..b048f72d 100644
--- a/swad_attendance.c
+++ b/swad_attendance.c
@@ -41,6 +41,7 @@
 #include "swad_pagination.h"
 #include "swad_parameter.h"
 #include "swad_photo.h"
+#include "swad_preference.h"
 #include "swad_QR.h"
 #include "swad_table.h"
 
@@ -77,7 +78,6 @@ typedef enum
 /*****************************************************************************/
 
 static void Att_ShowAllAttEvents (void);
-static void Att_PutFormToSelectWhichGroupsToShow (void);
 static void Att_ParamsWhichGroupsToShow (void);
 static void Att_PutIconsInListOfAttEvents (void);
 static void Att_PutIconToCreateNewAttEvent (void);
@@ -227,7 +227,11 @@ static void Att_ShowAllAttEvents (void)
 
    /***** Select whether show only my groups or all groups *****/
    if (Gbl.CurrentCrs.Grps.NumGrps)
-      Att_PutFormToSelectWhichGroupsToShow ();
+     {
+      Pre_StartPrefsHead ();
+      Grp_ShowFormToSelWhichGrps (ActSeeAtt,Att_ParamsWhichGroupsToShow);
+      Pre_EndPrefsHead ();
+     }
 
    if (Gbl.AttEvents.Num)
      {
@@ -294,16 +298,9 @@ static void Att_ShowAllAttEvents (void)
   }
 
 /*****************************************************************************/
-/***************** Put form to select which groups to show *******************/
+/***************** Put params to select which groups to show *****************/
 /*****************************************************************************/
 
-static void Att_PutFormToSelectWhichGroupsToShow (void)
-  {
-   fprintf (Gbl.F.Out,"<div style=\"display:table; margin:0 auto;\">");
-   Grp_ShowFormToSelWhichGrps (ActSeeAtt,Att_ParamsWhichGroupsToShow);
-   fprintf (Gbl.F.Out,"</div>");
-  }
-
 static void Att_ParamsWhichGroupsToShow (void)
   {
    Att_PutHiddenParamAttOrder ();
diff --git a/swad_calendar.c b/swad_calendar.c
index 2f1cb403..02a3777f 100644
--- a/swad_calendar.c
+++ b/swad_calendar.c
@@ -82,7 +82,9 @@ void Cal_PutIconsToSelectFirstDayOfWeek (void)
 
    Box_StartBox (NULL,Txt_Calendar,Cal_PutIconsFirstDayOfWeek,
                  Hlp_PROFILE_Preferences_calendar,Box_NOT_CLOSABLE);
+   Pre_StartPrefsHead ();
    Cal_ShowFormToSelFirstDayOfWeek (ActChg1stDay,NULL);
+   Pre_EndPrefsHead ();
    Box_EndBox ();
   }
 
@@ -108,7 +110,7 @@ void Cal_ShowFormToSelFirstDayOfWeek (Act_Action_t Action,void (*FuncParams) ())
    unsigned FirstDayOfWeek;
    char Icon[32 + 1];
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (FirstDayOfWeek = 0;	// Monday
 	FirstDayOfWeek <= 6;	// Sunday
 	FirstDayOfWeek++)
@@ -131,7 +133,7 @@ void Cal_ShowFormToSelFirstDayOfWeek (Act_Action_t Action,void (*FuncParams) ())
 	 Frm_EndForm ();
 	 fprintf (Gbl.F.Out,"</div>");
         }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
@@ -265,11 +267,15 @@ static void Cal_DrawCalendar (Act_Action_t ActionSeeCalendar,
 			      Gbl.CurrentDeg.Deg.DegCod,
 			      Gbl.CurrentCrs.Crs.CrsCod);
 
-   /***** Draw several months *****/
-   /* Show form to change first day of week */
+   /***** Preference selector to change first day of week *****/
    if (!PrintView)
+     {
+      Pre_StartPrefsHead ();
       Cal_ShowFormToSelFirstDayOfWeek (ActionChangeCalendar1stDay,NULL);
+      Pre_EndPrefsHead ();
+     }
 
+   /***** Draw several months *****/
    /* JavaScript will write HTML here */
    fprintf (Gbl.F.Out,"<div id=\"calendar\">"
 	              "</div>");
diff --git a/swad_changelog.h b/swad_changelog.h
index 38c90cdb..59001a45 100644
--- a/swad_changelog.h
+++ b/swad_changelog.h
@@ -429,10 +429,11 @@ En OpenSWAD:
 ps2pdf source.ps destination.pdf
 */
 
-#define Log_PLATFORM_VERSION	"SWAD 18.60 (2019-02-25)"
-#define CSS_FILE		"swad18.57.css"
+#define Log_PLATFORM_VERSION	"SWAD 18.60.1 (2019-02-25)"
+#define CSS_FILE		"swad18.60.1.css"
 #define JS_FILE			"swad18.60.js"
 /*
+	Version 18.60.1:  Feb 25, 2019 	Changes in CSS related to preferences. (237772 lines)
 	Version 18.60:    Feb 25, 2019 	Code refactoring in JavaScript code related to favs and shared. (237709 lines)
 	Version 18.59.2:  Feb 25, 2019 	Code refactoring related to favs and shared. (237677 lines)
 	Version 18.59.1:  Feb 25, 2019 	Optimization in JavaScript code related to favs and shared. (237785 lines)
@@ -440,15 +441,15 @@ ps2pdf source.ps destination.pdf
 	Version 18.58.1:  Feb 24, 2019 	Code cleaning related to AJAX and timeline.
 					Fixed bug in recent clicks. (237768 lines)
 					9 changes necessary in database:
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1512','es','N','Favorito public. social (global)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1513','es','N','Deshacer fav. public. social (global)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1514','es','N','Favorito public. social (usuario)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1515','es','N','Deshacer fav. public. social (usuario)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1516','es','N','Favorito coment. social (global)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1517','es','N','Deshacer fav. coment. social (global)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1518','es','N','Favorito coment. social (usuario)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1519','es','N','Deshacer fav. coment. social (usuario)');
-INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1520','es','N','Sugerir lista de usuarios a seguir');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1512','es','N','Marcar post social como favorito (global) ');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1513','es','N','Desmarcar post social como favorito (global)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1514','es','N','Marcar post social como favorito (usuario)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1515','es','N','Desmarcar post social como favorito (usuario)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1516','es','N','Marcar comentario social como favorito (global)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1517','es','N','Desmarcar comentario social como favorito (global)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1518','es','N','Marcar comentario social como favorito (usuario)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1519','es','N','Desmarcar comentario social como favorito (usuario)');
+INSERT INTO actions (ActCod,Language,Obsolete,Txt) VALUES ('1520','es','N','A qui&eacute;n seguir');
 
 	Version 18.58:    Feb 24, 2019 	Favourites in social comments are made in AJAX without reloading page. (237816 lines)
 	Version 18.57.3:  Feb 24, 2019 	Changes in social timeline related to AJAX and favourites. (237804 lines)
diff --git a/swad_game.c b/swad_game.c
index 4d5687fa..0fdd669d 100644
--- a/swad_game.c
+++ b/swad_game.c
@@ -41,6 +41,7 @@
 #include "swad_group.h"
 #include "swad_pagination.h"
 #include "swad_parameter.h"
+#include "swad_preference.h"
 #include "swad_role.h"
 #include "swad_table.h"
 #include "swad_test.h"
@@ -89,7 +90,6 @@ static void Gam_PutIconsListGames (void);
 static void Gam_PutIconToCreateNewGame (void);
 static void Gam_PutButtonToCreateNewGame (void);
 static void Gam_PutParamsToCreateNewGame (void);
-static void Gam_PutFormToSelectWhichGroupsToShow (void);
 static void Gam_ParamsWhichGroupsToShow (void);
 static void Gam_ShowOneGame (long GamCod,
                              bool ShowOnlyThisGame,
@@ -224,7 +224,11 @@ static void Gam_ListAllGames (void)
 
    /***** Select whether show only my groups or all groups *****/
    if (Gbl.CurrentCrs.Grps.NumGrps)
-      Gam_PutFormToSelectWhichGroupsToShow ();
+     {
+      Pre_StartPrefsHead ();
+      Grp_ShowFormToSelWhichGrps (ActSeeAllGam,Gam_ParamsWhichGroupsToShow);
+      Pre_EndPrefsHead ();
+     }
 
    if (Gbl.Games.Num)
      {
@@ -373,16 +377,9 @@ static void Gam_PutParamsToCreateNewGame (void)
   }
 
 /*****************************************************************************/
-/***************** Put form to select which groups to show *******************/
+/**************** Put params to select which groups to show ******************/
 /*****************************************************************************/
 
-static void Gam_PutFormToSelectWhichGroupsToShow (void)
-  {
-   fprintf (Gbl.F.Out,"<div style=\"display:table; margin:0 auto;\">");
-   Grp_ShowFormToSelWhichGrps (ActSeeAllGam,Gam_ParamsWhichGroupsToShow);
-   fprintf (Gbl.F.Out,"</div>");
-  }
-
 static void Gam_ParamsWhichGroupsToShow (void)
   {
    Gam_PutHiddenParamGameOrder ();
diff --git a/swad_group.c b/swad_group.c
index 7de0448e..8057c331 100644
--- a/swad_group.c
+++ b/swad_group.c
@@ -5010,7 +5010,7 @@ void Grp_ShowFormToSelWhichGrps (Act_Action_t Action,void (*FuncParams) ())
    extern const char *Txt_GROUP_WHICH_GROUPS[2];
    Grp_WhichGroups_t WhichGrps;
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (WhichGrps = Grp_ONLY_MY_GROUPS;
 	WhichGrps <= Grp_ALL_GROUPS;
 	WhichGrps++)
@@ -5028,7 +5028,7 @@ void Grp_ShowFormToSelWhichGrps (Act_Action_t Action,void (*FuncParams) ())
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
diff --git a/swad_icon.c b/swad_icon.c
index f46151f8..ba6cdf83 100644
--- a/swad_icon.c
+++ b/swad_icon.c
@@ -117,7 +117,8 @@ void Ico_PutIconsToSelectIconSet (void)
 
    Box_StartBox (NULL,Txt_Icons,Ico_PutIconsIconSet,
                  Hlp_PROFILE_Preferences_icons,Box_NOT_CLOSABLE);
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartPrefsHead ();
+   Pre_StartOnePrefSelector ();
    for (IconSet = (Ico_IconSet_t) 0;
 	IconSet < Ico_NUM_ICON_SETS;
 	IconSet++)
@@ -135,7 +136,8 @@ void Ico_PutIconsToSelectIconSet (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
+   Pre_EndPrefsHead ();
    Box_EndBox ();
   }
 
diff --git a/swad_menu.c b/swad_menu.c
index e301fa65..85fa327a 100644
--- a/swad_menu.c
+++ b/swad_menu.c
@@ -411,7 +411,8 @@ void Mnu_PutIconsToSelectMenu (void)
 
    Box_StartBox (NULL,Txt_Menu,Mnu_PutIconsMenu,
                  Hlp_PROFILE_Preferences_menu,Box_NOT_CLOSABLE);
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartPrefsHead ();
+   Pre_StartOnePrefSelector ();
    for (Menu = (Mnu_Menu_t) 0;
 	Menu < Mnu_NUM_MENUS;
 	Menu++)
@@ -425,7 +426,8 @@ void Mnu_PutIconsToSelectMenu (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
+   Pre_EndPrefsHead ();
    Box_EndBox ();
   }
 
diff --git a/swad_preference.c b/swad_preference.c
index 80b6318d..95ded300 100644
--- a/swad_preference.c
+++ b/swad_preference.c
@@ -235,7 +235,8 @@ static void Pre_PutIconsToSelectSideCols (void)
 
    Box_StartBox (NULL,Txt_Columns,Pre_PutIconsSideColumns,
                  Hlp_PROFILE_Preferences_columns,Box_NOT_CLOSABLE);
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartPrefsHead ();
+   Pre_StartOnePrefSelector ();
    for (SideCols = 0;
 	SideCols <= Lay_SHOW_BOTH_COLUMNS;
 	SideCols++)
@@ -252,7 +253,8 @@ static void Pre_PutIconsToSelectSideCols (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
+   Pre_EndPrefsHead ();
    Box_EndBox ();
   }
 
@@ -363,3 +365,36 @@ unsigned Pre_GetParamSideCols (void)
                                                Lay_SHOW_BOTH_COLUMNS,
                                                Cfg_DEFAULT_COLUMNS);
   }
+
+/*****************************************************************************/
+/********** Head to select one or several preferences using icons ************/
+/*****************************************************************************/
+/*
+                +-- Container for several pref. selectors ---+
+                |  +One pref.selector+  +One pref.selector+  |
+                |  | +-----+ +-----+ |  | +-----+ +-----+ |  |
+                |  | |Icon | |Icon | |  | |Icon | |Icon | |  |
+                |  | |opt.A| |opt.B| |  | |opt.A| |opt.B| |  |
+                |  | +-----+ +-----+ |  | +-----+ +-----+ |  |
+                |  +-----------------+  +-----------------+  |
+                +--------------------------------------------+
+*/
+void Pre_StartPrefsHead (void)
+  {
+   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINERS\">");
+  }
+
+void Pre_EndPrefsHead (void)
+  {
+   fprintf (Gbl.F.Out,"</div>");
+  }
+
+void Pre_StartOnePrefSelector (void)
+  {
+   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+  }
+
+void Pre_EndOnePrefSelector (void)
+  {
+   fprintf (Gbl.F.Out,"</div>");
+  }
diff --git a/swad_preference.h b/swad_preference.h
index 6dc40e35..8118145b 100644
--- a/swad_preference.h
+++ b/swad_preference.h
@@ -52,4 +52,9 @@ void Pre_ShowLeftCol (void);
 void Pre_ShowRightCol (void);
 unsigned Pre_GetParamSideCols (void);
 
+void Pre_StartPrefsHead (void);
+void Pre_EndPrefsHead (void);
+void Pre_StartOnePrefSelector (void);
+void Pre_EndOnePrefSelector (void);
+
 #endif
diff --git a/swad_project.c b/swad_project.c
index 3afc211e..88ef3c9f 100644
--- a/swad_project.c
+++ b/swad_project.c
@@ -41,6 +41,7 @@
 #include "swad_pagination.h"
 #include "swad_parameter.h"
 #include "swad_photo.h"
+#include "swad_preference.h"
 #include "swad_project.h"
 #include "swad_string.h"
 #include "swad_table.h"
@@ -266,6 +267,8 @@ static void Prj_ShowProjectsInCurrentPage (void)
                  Hlp_ASSESSMENT_Projects,Box_NOT_CLOSABLE);
 
    /***** Put forms to choice which projects to show *****/
+   /* 1st. row */
+   Pre_StartPrefsHead ();
    Prj_ShowFormToFilterByMy_All ();
    Prj_ShowFormToFilterByPreassignedNonPreassig ();
    switch (Gbl.Usrs.Me.Role.Logged)
@@ -278,6 +281,8 @@ static void Prj_ShowProjectsInCurrentPage (void)
       default:	// Students will see only visible projects
          break;
      }
+   Pre_EndPrefsHead ();
+   /* 2nd. row */
    Prj_ShowFormToFilterByDpt ();
 
    if (Gbl.Prjs.Num)
@@ -363,7 +368,7 @@ static void Prj_ShowFormToFilterByMy_All (void)
       "sitemap.svg",	// Prj_ALL_PROJECTS
      };
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (My_All =  (Prj_WhoseProjects_t) 0;
 	My_All <= (Prj_WhoseProjects_t) (Prj_NUM_WHOSE_PROJECTS - 1);
 	My_All++)
@@ -385,7 +390,7 @@ static void Prj_ShowFormToFilterByMy_All (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
@@ -398,7 +403,7 @@ static void Prj_ShowFormToFilterByPreassignedNonPreassig (void)
    struct Prj_Filter Filter;
    Prj_PreassignedNonpreassig_t PreNon;
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (PreNon =  (Prj_PreassignedNonpreassig_t) 0;
 	PreNon <= (Prj_PreassignedNonpreassig_t) (Prj_NUM_PREASSIGNED_NONPREASSIG - 1);
 	PreNon++)
@@ -420,7 +425,7 @@ static void Prj_ShowFormToFilterByPreassignedNonPreassig (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
@@ -438,7 +443,7 @@ static void Prj_ShowFormToFilterByHidden (void)
       "eye.svg",	// Prj_VISIBL
      };
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartOnePrefSelector ();
    for (HidVis =  (Prj_HiddenVisibl_t) 0;
 	HidVis <= (Prj_HiddenVisibl_t) (Prj_NUM_HIDDEN_VISIBL - 1);
 	HidVis++)
@@ -460,7 +465,7 @@ static void Prj_ShowFormToFilterByHidden (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
   }
 
 /*****************************************************************************/
diff --git a/swad_social.c b/swad_social.c
index cf8af89b..2b5d3ffe 100644
--- a/swad_social.c
+++ b/swad_social.c
@@ -968,7 +968,9 @@ static void Soc_ShowTimeline (char *Query,
 				Query);
 
    /***** Start box *****/
-   Box_StartBox (Soc_WIDTH_TIMELINE,Title,Soc_PutIconsTimeline,
+   // Box_StartBox (Soc_WIDTH_TIMELINE,Title,Soc_PutIconsTimeline,
+   //               Hlp_SOCIAL_Timeline,Box_NOT_CLOSABLE);
+   Box_StartBox (NULL,Title,Soc_PutIconsTimeline,
                  Hlp_SOCIAL_Timeline,Box_NOT_CLOSABLE);
 
    /***** Put form to select users whom public activity is displayed *****/
@@ -1120,7 +1122,9 @@ static void Soc_PutFormWhichUsrs (void)
       "users.svg",	// Soc_USRS_ALL
      };
 
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   /***** Preference selector for which users *****/
+   Pre_StartPrefsHead ();
+   Pre_StartOnePrefSelector ();
    for (WhichUsrs = (Soc_WhichUsrs_t) 1;
 	WhichUsrs < Soc_NUM_WHICH_USRS;
 	WhichUsrs++)
@@ -1134,7 +1138,8 @@ static void Soc_PutFormWhichUsrs (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
+   Pre_EndPrefsHead ();
 
    /***** Show warning if I do not follow anyone *****/
    if (Gbl.Social.WhichUsrs == Soc_USRS_FOLLOWED)
diff --git a/swad_survey.c b/swad_survey.c
index 535d3566..4b6f1b93 100644
--- a/swad_survey.c
+++ b/swad_survey.c
@@ -40,6 +40,7 @@
 #include "swad_notification.h"
 #include "swad_pagination.h"
 #include "swad_parameter.h"
+#include "swad_preference.h"
 #include "swad_role.h"
 #include "swad_survey.h"
 #include "swad_table.h"
@@ -98,7 +99,6 @@ static void Svy_PutIconsListSurveys (void);
 static void Svy_PutIconToCreateNewSvy (void);
 static void Svy_PutButtonToCreateNewSvy (void);
 static void Svy_PutParamsToCreateNewSvy (void);
-static void Svy_PutFormToSelectWhichGroupsToShow (void);
 static void Svy_ParamsWhichGroupsToShow (void);
 static void Svy_ShowOneSurvey (long SvyCod,struct SurveyQuestion *SvyQst,
                                bool ShowOnlyThisSvyComplete);
@@ -229,7 +229,11 @@ static void Svy_ListAllSurveys (struct SurveyQuestion *SvyQst)
 
    /***** Select whether show only my groups or all groups *****/
    if (Gbl.CurrentCrs.Grps.NumGrps)
-      Svy_PutFormToSelectWhichGroupsToShow ();
+     {
+      Pre_StartPrefsHead ();
+      Grp_ShowFormToSelWhichGrps (ActSeeAllSvy,Svy_ParamsWhichGroupsToShow);
+      Pre_EndPrefsHead ();
+     }
 
    if (Gbl.Svys.Num)
      {
@@ -375,16 +379,9 @@ static void Svy_PutParamsToCreateNewSvy (void)
   }
 
 /*****************************************************************************/
-/***************** Put form to select which groups to show *******************/
+/**************** Put params to select which groups to show ******************/
 /*****************************************************************************/
 
-static void Svy_PutFormToSelectWhichGroupsToShow (void)
-  {
-   fprintf (Gbl.F.Out,"<div style=\"display:table; margin:0 auto;\">");
-   Grp_ShowFormToSelWhichGrps (ActSeeAllSvy,Svy_ParamsWhichGroupsToShow);
-   fprintf (Gbl.F.Out,"</div>");
-  }
-
 static void Svy_ParamsWhichGroupsToShow (void)
   {
    Svy_PutHiddenParamSvyOrder ();
diff --git a/swad_theme.c b/swad_theme.c
index b294d500..0f317c8d 100644
--- a/swad_theme.c
+++ b/swad_theme.c
@@ -268,7 +268,8 @@ void The_PutIconsToSelectTheme (void)
 
    Box_StartBox (NULL,Txt_Theme_SKIN,The_PutIconsTheme,
                  Hlp_PROFILE_Preferences_theme,Box_NOT_CLOSABLE);
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartPrefsHead ();
+   Pre_StartOnePrefSelector ();
    for (Theme = (The_Theme_t) 0;
 	Theme < The_NUM_THEMES;
 	Theme++)
@@ -286,7 +287,8 @@ void The_PutIconsToSelectTheme (void)
       Frm_EndForm ();
       fprintf (Gbl.F.Out,"</div>");
      }
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
+   Pre_EndPrefsHead ();
    Box_EndBox ();
   }
 
diff --git a/swad_timetable.c b/swad_timetable.c
index a4720bf0..bfdb435c 100644
--- a/swad_timetable.c
+++ b/swad_timetable.c
@@ -38,6 +38,7 @@
 #include "swad_global.h"
 #include "swad_language.h"
 #include "swad_parameter.h"
+#include "swad_preference.h"
 #include "swad_timetable.h"
 
 /*****************************************************************************/
@@ -370,15 +371,20 @@ void TT_ShowClassTimeTable (void)
       TT_ShowTimeTableGrpsSelected ();
    else
      {
-      /***** Select whether show only my groups or all groups *****/
+      /***** Preference selector *****/
+      Pre_StartPrefsHead ();
+
+      /* Select whether show only my groups or all groups */
       if ( Gbl.TimeTable.Type == TT_MY_TIMETABLE ||
           (Gbl.TimeTable.Type == TT_COURSE_TIMETABLE &&
            Gbl.CurrentCrs.Grps.NumGrps))
          TT_PutFormToSelectWhichGroupsToShow ();
 
-      /***** Show form to change first day of week *****/
+      /* Show form to change first day of week */
       Cal_ShowFormToSelFirstDayOfWeek (ActChgTT1stDay[Gbl.TimeTable.Type],
                                        Grp_PutParamWhichGrps);
+
+      Pre_EndPrefsHead ();
      }
 
    /***** Show the time table *****/
diff --git a/swad_user.c b/swad_user.c
index 83ec57ad..96c8ce31 100644
--- a/swad_user.c
+++ b/swad_user.c
@@ -5859,7 +5859,8 @@ void Usr_FreeListOtherRecipients (void)
 
 void Usr_ShowFormsToSelectUsrListType (Act_Action_t NextAction)
   {
-   fprintf (Gbl.F.Out,"<div class=\"PREF_CONTAINER\">");
+   Pre_StartPrefsHead ();
+   Pre_StartOnePrefSelector ();
 
    /***** Select Usr_LIST_AS_CLASS_PHOTO *****/
    fprintf (Gbl.F.Out,"<div class=\"%s\">",
@@ -5892,7 +5893,8 @@ void Usr_ShowFormsToSelectUsrListType (Act_Action_t NextAction)
    Frm_EndForm ();
    fprintf (Gbl.F.Out,"</div>");
 
-   fprintf (Gbl.F.Out,"</div>");
+   Pre_EndOnePrefSelector ();
+   Pre_EndPrefsHead ();
   }
 
 /*****************************************************************************/