docs: function(ordinal){
          var cellNodes = this._cellNodes,
              n = cellNodes.length,
              index = Math.min(ordinal, n-1),
              cellOrdinal, node
          ;
          while(index >= 0) {
              //get the node at the current index
              node = cellNodes[index];
              cellOrdinal = this._getCellOrdinal(node);
              if (cellOrdinal === ordinal) {
                return index;
              }
              else
              if (cellOrdinal > ordinal) {
                index--;
              }
              else {
                return -1;
              }
          }
          return -1;
      }