anchor.diff:  			   var checkbox = document.getElementById(checkbox_name);
   			   if(checkbox != null) {
   			   	checkbox.checked = 1;
  +			   } else {
  +			        alert("checkbox == null???");
   			   }
   			}
  -	        }
  +	        } 
   	    }
   	}
   
  
positive.code:   <script type="text/javascript">
    
  	function checkAll() {
  	
  	alert("checkAll");
  	
  	    var size = document.getElementById("size");
        	    var size_str = size.value;
  	    var m = parseInt(size_str);
  	    
  alert("checkAll " + m);	    
  	    
  	    var i;
  	    var j;
  	    for (i=0; i<m; i++) {
  	        var checkbox_size_name = "checkbox_size_" + i;
  	        
  	        alert(checkbox_size_name);
  	        
  	        
  	        if (document.getElementById(checkbox_size_name) != null) {
  			var checkbox_size_value = document.getElementById(checkbox_size_name).value;
  			var n = parseInt(checkbox_size_value);
  
negative.code:                    String checkbox_size_value =  new Integer(selected_matches.size()).toString();
                     
   %>                  
       <input type="hidden" name="<%=checkbox_size_name%>" id="<%=checkbox_size_name%>" value="<%=checkbox_size_value%>" />
   <%                  
                     
                     
  