diff --git a/subnets.html b/subnets.html
index 9b5bc87..09a6201 100644
--- a/subnets.html
+++ b/subnets.html
@@ -4,18 +4,9 @@
 <script language="javascript" type="text/javascript">
 <!--
 
-var visibleColumns = {
-  subnet: true,
-  netmask: false,
-  range: true,
-  useable: true,
-  hosts: true,
-  divide: true,
-  join: true,
-};
-
 var curNetwork = 0;
 var curMask = 0;
+var curComments = {};
 
 function updateNetwork()
 {
@@ -69,12 +60,6 @@ function startOver()
 
 function recreateTables()
 {
-  // Update header visibility
-  for (const name in visibleColumns) {
-    console.log(name)
-    document.getElementById(name + 'Header').style.display = visibleColumns[name] ? 'table-cell' : 'none';
-  }
-
   var calcbody = document.getElementById('calcbody');
   if (!calcbody) {
     alert('Body not found');
@@ -91,12 +76,39 @@ function recreateTables()
   createRow(calcbody, rootSubnet, curNetwork, curMask, [curMask, rootSubnet[1], rootSubnet], rootSubnet[0]);
 
   document.getElementById('joinHeader').colSpan = (rootSubnet[0] > 0 ? rootSubnet[0] : 1);
-//  document.getElementById('col_join').span = (rootSubnet[0] > 0 ? rootSubnet[0] : 1);
+  document.getElementById('col_join').span = (rootSubnet[0] > 0 ? rootSubnet[0] : 1);
 
-  /* Create the bookmark hyperlink */
+  /* Disable joins for subnets with comments. */
+  var joinLocks = {}; // a unique collection of join elements to disable
+
+  for (var addressWithMask in curComments) {
+    let splitAddressMask = addressWithMask.split('/');
+    let addressToLock = inet_aton(splitAddressMask[0]);
+    let upperMaskToLock = splitAddressMask[1];
+    for (let maskToLock = upperMaskToLock; maskToLock >= curMask; maskToLock--) {
+      joinLocks[inet_ntoa(network_address(addressToLock, maskToLock)) + "/" + maskToLock] = true;
+    }
+  }
+
+  for (var lock in joinLocks) {
+    let joinElement = document.getElementById("join_" + lock);
+    if (joinElement && joinElement.onclick) {
+      joinElement.onclick = null;
+      joinElement.classList.remove("maskSpanJoinable");
+      joinElement.classList.add("maskSpan");
+    }
+  };
+
+  createBookmarkHyperlink();
+}
+
+function createBookmarkHyperlink() {
   var link = document.getElementById('saveLink');
   if (link) {
-    link.href = 'subnets.html?network='+inet_ntoa(curNetwork)+'&mask='+curMask+'&division='+binToAscii(nodeToString(rootSubnet));
+    link.href = '?network='+inet_ntoa(curNetwork)
+               +'&mask='+curMask
+               +'&division='+binToAscii(nodeToString(rootSubnet))
+               +'&comments='+encodeURIComponent(JSON.stringify(curComments));
   }
 }
 
@@ -148,9 +160,10 @@ function asciiToBin(str)
   return out;
 }
 
+// Recursive function that creates rows working from the outer most mask and working inwards
 function createRow(calcbody, node, address, mask, labels, depth)
 {
-  if (node[2]) {
+  if (node[2]) { // We need to go deeper
     var newlabels = labels;
     newlabels.push(mask+1);
     newlabels.push(node[2][0][1]);
@@ -163,16 +176,14 @@ function createRow(calcbody, node, address, mask, labels, depth)
     newlabels.push(node[2][1]);
     createRow(calcbody, node[2][1], address+subnet_addresses(mask+1), mask+1, newlabels, depth-1);
   }
-  else {
+  else { // Actually create a row
     var newRow = document.createElement('TR');
     calcbody.appendChild(newRow);
 
     /* subnet address */
-    if (visibleColumns.subnet) {
-      var newCell = document.createElement('TD');
-      newCell.appendChild(document.createTextNode(inet_ntoa(address)+'/'+mask));
-      newRow.appendChild(newCell);
-    }
+    var newCell = document.createElement('TD');
+    newCell.appendChild(document.createTextNode(inet_ntoa(address)+'/'+mask));
+    newRow.appendChild(newCell);
 
     var addressFirst = address;
     var addressLast = subnet_last_address(address, mask);
@@ -181,6 +192,7 @@ function createRow(calcbody, node, address, mask, labels, depth)
     var numHosts;
     var addressRange;
     var usaebleRange;
+    var comment = curComments[inet_ntoa(address) + "/" + mask] || null;
 
     if (mask == 32) {
       addressRange = inet_ntoa(addressFirst);
@@ -200,91 +212,112 @@ function createRow(calcbody, node, address, mask, labels, depth)
     }
 
     /* netmask */
-    if (visibleColumns.netmask) {
-      var newCell = document.createElement('TD');
-      newCell.appendChild(document.createTextNode(inet_ntoa(subnet_netmask(mask))));
-      newRow.appendChild(newCell);
-    }
+    var newCell = document.createElement('TD');
+    newCell.appendChild(document.createTextNode(inet_ntoa(subnet_netmask(mask))));
+    newRow.appendChild(newCell);
 
     /* range of addresses */
-    if (visibleColumns.range) {
-      var newCell = document.createElement('TD');
-      newCell.appendChild(document.createTextNode(addressRange));
-      newRow.appendChild(newCell);
-    }
+    var newCell = document.createElement('TD');
+    newCell.appendChild(document.createTextNode(addressRange));
+    newRow.appendChild(newCell);
 
     /* useable addresses */
-    if (visibleColumns.useable) {
-      var newCell = document.createElement('TD');
-      newCell.appendChild(document.createTextNode(useableRange));
-      newRow.appendChild(newCell);
-    }
+    var newCell = document.createElement('TD');
+    newCell.appendChild(document.createTextNode(useableRange));
+    newRow.appendChild(newCell);
 
     /* Hosts */
-    if (visibleColumns.hosts) {
-      var newCell = document.createElement('TD');
-      newCell.appendChild(document.createTextNode(numHosts));
-      newRow.appendChild(newCell);
-    }
+    var newCell = document.createElement('TD');
+    newCell.appendChild(document.createTextNode(numHosts));
+    newRow.appendChild(newCell);
+
+    /* Comments */
+    var newCell = document.createElement('TD');
+    var textarea = document.createElement('TEXTAREA');
+    textarea.id = "comment_" + inet_ntoa(network_address(address, mask)) + "/" + mask;
+    textarea.onchange = ((mask, address) => ( function() {
+      var key = inet_ntoa(address) + "/" + mask;
+      var needToRedraw = false;
+
+      if (this.value == null || this.value === "") {
+        needToRedraw = curComments[key] !== undefined;
+        delete curComments[key];
+      } else {
+        needToRedraw = curComments[key] === undefined;
+        curComments[key] = this.value;
+      }
+
+      if (needToRedraw) {
+        recreateTables();
+        // Restore previous focus after redrawing table
+        document.getElementById(this.id).focus();
+      } else {
+        // Just update link if we don't need to redraw.
+        createBookmarkHyperlink();
+      }
+    }))(mask, address); // keep some vars in scope
+
+    textarea.innerText = comment;
+    newCell.appendChild(textarea);
+    newRow.appendChild(newCell);
 
     /* actions */
 
-    if (visibleColumns.divide) {
-      var newCell = document.createElement('TD');
-      newRow.appendChild(newCell);
+    var newCell = document.createElement('TD');
+    newRow.appendChild(newCell);
 
-      if (mask == 32) {
-	var newLink = document.createElement('SPAN');
-	newLink.className = 'disabledAction';
-	newLink.appendChild(document.createTextNode('Divide'));
-	newCell.appendChild(newLink);
+    if (mask == 32 || comment != null) {
+      var newLink = document.createElement('SPAN');
+      newLink.className = 'disabledAction';
+      newLink.appendChild(document.createTextNode('Divide'));
+      newCell.appendChild(newLink);
+    }
+    else {
+      var newLink = document.createElement('A');
+      newLink.href = '#';
+      newLink.onclick = function () { divide(node); return false; }
+      newLink.appendChild(document.createTextNode('Divide'));
+      newCell.appendChild(newLink);
+    }
+
+    var colspan = depth - node[0];
+
+    for (var i=(labels.length/3)-1; i>=0; i--) {
+      var mask = labels[i*3];
+      var rowspan = labels[(i*3)+1];
+      var joinnode = labels[(i*3)+2];
+
+      var newCell = document.createElement('TD');
+      newCell.rowSpan = (rowspan > 1 ? rowspan : 1);
+      newCell.colSpan = (colspan > 1 ? colspan : 1);
+      newCell.id = "join_" + inet_ntoa(network_address(address, mask)) + "/" + mask;
+
+      if (i == (labels.length/3)-1) {
+	newCell.className = 'maskSpan';
       }
       else {
-	var newLink = document.createElement('A');
-	newLink.href = '#';
-	newLink.onclick = function () { divide(node); return false; }
-	newLink.appendChild(document.createTextNode('Divide'));
-	newCell.appendChild(newLink);
+	newCell.className = 'maskSpanJoinable';
+	newCell.onclick = newJoin(joinnode);
+	//	newCell.onmouseover = function() { window.status = joinnode[0]+'---'+joinnode[1]+'---'+joinnode[2]+'>>>>>'+node[2];}
       }
-    }
 
-    if (visibleColumns.join) {
-      var colspan = depth - node[0];
+      var newImg = document.createElement('IMG');
+      newImg.src = 'img/'+mask+'.gif';
+      newCell.appendChild(newImg);
+      newRow.appendChild(newCell);
 
-      for (var i=(labels.length/3)-1; i>=0; i--) {
-	var mask = labels[i*3];
-	var rowspan = labels[(i*3)+1];
-	var joinnode = labels[(i*3)+2];
-
-	var newCell = document.createElement('TD');
-	newCell.rowSpan = (rowspan > 1 ? rowspan : 1);
-	newCell.colSpan = (colspan > 1 ? colspan : 1);
-
-	if (i == (labels.length/3)-1) {
-	  newCell.className = 'maskSpan';
-	}
-	else {
-	  newCell.className = 'maskSpanJoinable';
-	  newCell.onclick = newJoin(joinnode);
-	  //	newCell.onmouseover = function() { window.status = joinnode[0]+'---'+joinnode[1]+'---'+joinnode[2]+'>>>>>'+node[2];}
-	}
-
-	var newImg = document.createElement('IMG');
-	newImg.src = 'img/'+mask+'.gif';
-	newCell.appendChild(newImg);
-	newRow.appendChild(newCell);
-
-	colspan = 1; // reset for subsequent cells
-      }
+      colspan = 1; // reset for subsequent cells
     }
   }
-
 }
 
 /* This is necessary because 'joinnode' changes during the scope of the caller */
 function newJoin(joinnode)
 {
-  return function() { join(joinnode) };
+  return function() {
+    join(joinnode);
+    return false; // prevent click event
+  };
 }
 
 function divide(node)
@@ -370,7 +403,7 @@ function network_address(ip, mask)
 
 function subnet_addresses(mask)
 {
-  return 2**(32-mask);
+  return 1<<(32-mask);
 }
 
 function subnet_last_address(subnet, mask)
@@ -407,6 +440,12 @@ function calcOnLoad()
   if (args['network'] && args['mask'] && args['division']) {
     document.forms['calc'].elements['network'].value = args['network'];
     document.forms['calc'].elements['netbits'].value = args['mask'];
+
+    if (args['comments']) {
+      curComments = JSON.parse(args['comments']);
+    } else {
+      curComments = {};
+    }
     updateNetwork();
     var division = asciiToBin(args['division']);
     rootSubnet = [0, 0, null];
@@ -458,18 +497,14 @@ window.onload = calcOnLoad;
 function toggleColumn(cb)
 {
   var colName = 'col_'+(cb.id.substr(3));
-//  var col = document.getElementById(colName);
+  var col = document.getElementById(colName);
 
-  visibleColumns[cb.id.substr(3)] = cb.checked;
-
-//  if (cb.checked) {
-//    col.style.display = 'table-column';
-//    col.style.visibility = 'visible';
-//  }
-//  else {
-//    col.style.display = 'none';
-//    col.style.visibility = 'collapse';
-//  }
+  if (cb.checked) {
+    col.style.display = 'block';
+  }
+  else {
+    col.style.display = 'none';
+  }
   recreateTables(); /* because IE draws lines all over the place with border-collapse */
 }
 
@@ -492,7 +527,8 @@ P		{
   font-size: 75%;
 }
 
-.label {
+
+.label		{
   font-family: Arial, Verdana, sans-serif;
   font-size: 60%;
 }
@@ -502,8 +538,7 @@ P		{
   font-size: 80%;
   border-collapse: collapse; 
 }
-
-.calc td, .calc th {
+.calc td {
  border: 1px solid black;
 }
 
@@ -512,6 +547,10 @@ P		{
   background-color: #eeeeee;
 }
 
+.calc textarea {
+  height: 1.5em;
+}
+
 .disabledAction {
  color: #dddddd;
 }
@@ -523,7 +562,7 @@ P		{
 .maskSpanJoinable {
   background-color: #cccccc;
   text-align: right;
- cursor: pointer;
+  cursor: grab;
 }
 
 .maskSpanRotate {
@@ -559,12 +598,13 @@ P		{
 </tr>
 </table>
 
-<p>Show columns: 
+<p>Show columns:
 <input type="checkbox" id="cb_subnet" checked onclick="toggleColumn(this)"><label for="cb_subnet">Subnet address</label>
 <input type="checkbox" id="cb_netmask" onclick="toggleColumn(this)"><label for="cb_netmask">Netmask</label>
 <input type="checkbox" id="cb_range" checked onclick="toggleColumn(this)"><label for="cb_range">Range of addresses</label>
 <input type="checkbox" id="cb_useable" checked onclick="toggleColumn(this)"><label for="cb_useable">Useable IPs</label>
 <input type="checkbox" id="cb_hosts" checked onclick="toggleColumn(this)"><label for="cb_hosts">Hosts</label>
+<input type="checkbox" id="cb_comments" checked onclick="toggleColumn(this)"><label for="cb_comments">Comments</label>
 <input type="checkbox" id="cb_divide" checked onclick="toggleColumn(this)"><label for="cb_divide">Divide</label>
 <input type="checkbox" id="cb_join" checked onclick="toggleColumn(this)"><label for="cb_join">Join</label>
 </p>
@@ -575,7 +615,7 @@ If you wish to save this subnetting for later, bookmark <a href="subnets.html" i
 
 </td>
 <td align="right">
-<a href="https://github.com/davidc/subnets"><img alt="Fork me on GitHub" src="https://github.blog/wp-content/uploads/2008/12/forkme_right_white_ffffff.png" style="right: 0;top: 0;position: absolute;"></a>
+<a href="https://github.com/davidc/subnets"><img alt="Fork me on GitHub" src="https://github.blog/wp-content/uploads/2008/12/forkme_right_white_ffffff.png" style="right: 0;top: 0;position: absolute;" ></a>
 </td>
 </tr>
 </table>
@@ -585,15 +625,26 @@ If you wish to save this subnetting for later, bookmark <a href="subnets.html" i
 <br>
 
 <table class="calc" cellspacing="0" cellpadding="2">
+<colgroup>
+<col id="col_subnet">
+<col id="col_netmask" style="display: none">
+<col id="col_range">
+<col id="col_useable">
+<col id="col_hosts">
+<col id="col_comments">
+<col id="col_divide">
+<col id="col_join">
+</colgroup>
 <thead>
 <tr>
-<th id="subnetHeader">Subnet address</th>
-<th id="netmaskHeader">Netmask</th>
-<th id="rangeHeader">Range of addresses</th>
-<th id="useableHeader">Useable IPs</th>
-<th id="hostsHeader">Hosts</th>
-<th id="divideHeader">Divide</th>
-<th id="joinHeader">Join</th>
+<td>Subnet address</td>
+<td>Netmask</td>
+<td>Range of addresses</td>
+<td>Useable IPs</td>
+<td>Hosts</td>
+<td>Comments</td>
+<td>Divide</td>
+<td id="joinHeader">Join</td>
 </tr>
 </thead>
 <tbody id="calcbody">