diff --git a/addons/hr_timesheet_sheet/hr_timesheet_sheet.py b/addons/hr_timesheet_sheet/hr_timesheet_sheet.py
index 12eae4e6ba2..c62bbfb2b57 100644
--- a/addons/hr_timesheet_sheet/hr_timesheet_sheet.py
+++ b/addons/hr_timesheet_sheet/hr_timesheet_sheet.py
@@ -65,7 +65,7 @@ class hr_timesheet_sheet(osv.osv):
     def create(self, cr, uid, vals, *args, **argv):
         if 'employee_id' in vals:
             if not self.pool.get('hr.employee').browse(cr, uid, vals['employee_id']).user_id:
-                raise osv.except_osv(_('Error!'), _('In order to create a timesheet for this employee, you must relate a user to it.'))
+                raise osv.except_osv(_('Error!'), _('In order to create a timesheet for this employee, you must link an employee to a user.'))
             if not self.pool.get('hr.employee').browse(cr, uid, vals['employee_id']).product_id:
                 raise osv.except_osv(_('Error!'), _('In order to create a timesheet for this employee, you must link the employee to a product, like \'Consultant\'.'))
             if not self.pool.get('hr.employee').browse(cr, uid, vals['employee_id']).journal_id:
@@ -76,7 +76,7 @@ class hr_timesheet_sheet(osv.osv):
         if 'employee_id' in vals:
             new_user_id = self.pool.get('hr.employee').browse(cr, uid, vals['employee_id']).user_id.id or False
             if not new_user_id:
-                raise osv.except_osv(_('Error!'), _('In order to create a timesheet for this employee, you must relate a user to it.'))
+                raise osv.except_osv(_('Error!'), _('In order to create a timesheet for this employee, you must link an employee to a user.'))
             if not self._sheet_date(cr, uid, ids, forced_user_id=new_user_id):
                 raise osv.except_osv(_('Error!'), _('You cannot have 2 timesheets that overlap!\nYou should use the menu \'My Timesheet\' to avoid this problem.'))
             if not self.pool.get('hr.employee').browse(cr, uid, vals['employee_id']).product_id:
diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index e570a73a539..09cdcd4e4d5 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -476,7 +476,7 @@ class purchase_order(osv.osv):
             if not acc_id:
                 acc_id = po_line.product_id.categ_id.property_account_expense_categ.id
             if not acc_id:
-                raise osv.except_osv(_('Error!'), _('Define expense account for this product: "%s" (id:%d).') % (po_line.product_id.name, po_line.product_id.id,))
+                raise osv.except_osv(_('Error!'), _('Define an expense account for this product: "%s" (id:%d).') % (po_line.product_id.name, po_line.product_id.id,))
         else:
             acc_id = property_obj.get(cr, uid, 'property_account_expense_categ', 'product.category', context=context).id
         fpos = po_line.order_id.fiscal_position or False
diff --git a/addons/purchase_requisition/wizard/purchase_requisition_partner.py b/addons/purchase_requisition/wizard/purchase_requisition_partner.py
index 5aeb2c82ab6..a71b53e5ee9 100644
--- a/addons/purchase_requisition/wizard/purchase_requisition_partner.py
+++ b/addons/purchase_requisition/wizard/purchase_requisition_partner.py
@@ -38,7 +38,7 @@ class purchase_requisition_partner(osv.osv_memory):
         record_id = context and context.get('active_id', False) or False
         tender = self.pool.get('purchase.requisition').browse(cr, uid, record_id, context=context)
         if not tender.line_ids:
-            raise osv.except_osv(_('Error!'), _('No Product in Requisition.'))
+            raise osv.except_osv(_('Error!'), _('Define products you want include in the call for bids.'))
         return res
 
     def create_order(self, cr, uid, ids, context=None):