anchor.diff:  
   function addActivityRow() {
       var activity = selectedActivity()
  +    if (!activity.id || !activity.name) return
       var cells = []
       var dayCount = ${period.dayRanges[0].days}.length
       var rowCount = $$("#input-body tr").length - 1
  
positive.code:                     <c:forEach items="${period.dayRanges[0].days}" var="d">
                          <th id="day-number" class="day-number">
                              <c:forEach begin="0" end="${period.repetitions - 1}" var="x" varStatus="xStatus">
                                  <c:set var="visibleRow" value="${x lt MAX_REPETITIONS_DISPLAYED_WHEN_COMPRESSED}"/>
                                  <c:set var="showCompressionRow" value="${x eq (MAX_REPETITIONS_DISPLAYED_WHEN_COMPRESSED)}"/>
  
                                  <c:if test="${not compressPeriod or visibleRow or xStatus.last}">
                                      ${d + x * period.duration.days}
                                  </c:if>
  
                                  <c:if test="${compressPeriod and not visibleRow and showCompressionRow and not xStatus.last}">
                                      .
                                  </c:if>
  
  
negative.code:         cursor:pointer;
      }
  
      .limited-display-box {
          width:500px;
          overflow:scroll;
          /*display:block;*/
      }
  
  </style>
  </head>
  <body>
  