function getCenterWidth() {
      var width = window.innerWidth;

      if (width == null) {
         width = document.body.offsetWidth;
      }
      
      return width / 2;
   }
   
   function getCenterHeight() {
      var height = window.innerHeight;

      if (height == null) {
         height = document.body.offsetHeight;
      }

      return height / 2;
   }

   function showVoteForm() {
      document.getElementById('_comments4Cocktail').style.visibility='hidden';
      document.getElementById('_rememberCocktail').style.visibility='hidden';
      document.getElementById('_proposeCocktail').style.visibility='hidden';
      document.getElementById('_commentCocktail').style.visibility='hidden';

      document.getElementById('_vote4Cocktail').style.left = getCenterWidth() - 115;
      document.getElementById('_vote4Cocktail').style.top = getCenterHeight() - 30;
      document.getElementById('_vote4Cocktail').style.visibility='visible';
   }

   function showCommentForm() {
      document.getElementById('_vote4Cocktail').style.visibility='hidden';
      document.getElementById('_comments4Cocktail').style.visibility='hidden';
      document.getElementById('_rememberCocktail').style.visibility='hidden';
      document.getElementById('_proposeCocktail').style.visibility='hidden';

      document.getElementById('_commentCocktail').style.left = getCenterWidth() - 310;
      document.getElementById('_commentCocktail').style.top = getCenterHeight() + 15;
      document.getElementById('_commentCocktail').style.visibility='visible';
   }

   function showAllComments() {
      document.getElementById('_vote4Cocktail').style.visibility='hidden';
      document.getElementById('_rememberCocktail').style.visibility='hidden';
      document.getElementById('_proposeCocktail').style.visibility='hidden';
      document.getElementById('_commentCocktail').style.visibility='hidden';

      document.getElementById('_comments4Cocktail').style.left = getCenterWidth() - 210;
      document.getElementById('_comments4Cocktail').style.top = getCenterHeight() - 180;
      document.getElementById('_comments4Cocktail').style.visibility='visible';
   }
   
   function showRememberForm() {
      document.getElementById('_vote4Cocktail').style.visibility='hidden';
      document.getElementById('_comments4Cocktail').style.visibility='hidden';
      document.getElementById('_proposeCocktail').style.visibility='hidden';
      document.getElementById('_commentCocktail').style.visibility='hidden';

      document.getElementById('_rememberCocktail').style.left = getCenterWidth() - 210;
      document.getElementById('_rememberCocktail').style.top = getCenterHeight() - 100;
      document.getElementById('_rememberCocktail').style.visibility='visible';
   }

   function showProposeForm() {
      document.getElementById('_vote4Cocktail').style.visibility='hidden';
      document.getElementById('_comments4Cocktail').style.visibility='hidden';
      document.getElementById('_rememberCocktail').style.visibility='hidden';
      document.getElementById('_commentCocktail').style.visibility='hidden';
      
      document.getElementById('_proposeCocktail').style.left = getCenterWidth() - 310;
      document.getElementById('_proposeCocktail').style.top = getCenterHeight() + 60;
      document.getElementById('_proposeCocktail').style.visibility='visible';
   }