diff --git a/frontend/index.html b/frontend/index.html
index 32add7a..ccda4ce 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -32,7 +32,6 @@
 
 <div id="content">
 	<div id="plot"></div>
-	
 	<table id="move">
 		<tr>
 			<td>
diff --git a/frontend/javascripts/entity.js b/frontend/javascripts/entity.js
index 098852c..524f97b 100644
--- a/frontend/javascripts/entity.js
+++ b/frontend/javascripts/entity.js
@@ -25,7 +25,8 @@
  */
 
 /**
- * Entity
+ * Entity constructor
+ * @todo add validation
  */
 var Entity = function(json) {
 	for (var i in json) {
@@ -48,9 +49,8 @@ var Entity = function(json) {
 
 /**
  * Show and edit entity details
- * @param entity
  */
-Entity.prototype.showDetails = function(entity) {
+Entity.prototype.showDetails = function() {
 	$('<div>')
 	.addClass('details')
 	.append(this.getDOM())
@@ -63,10 +63,9 @@ Entity.prototype.showDetails = function(entity) {
 /**
  * Show from for new Channel
  * 
- * @param type
- * @todo
+ * @todo implement/test
  */
-Entity.prototype.getDOM = function(type) {
+Entity.prototype.getDOM = function() {
 	var properties = $('<table><thead><th>Key</th><th>Value</th></thead></table');
 	
 	$.each(entity, function(key, value) {
@@ -106,7 +105,12 @@ Entity.prototype.getDOM = function(type) {
 	// TODO optional properties
 };
 
-Entity.prototype.validate = function(entity) {
+/**
+ * Validate Entity for required and optional properties and their values
+ * @return boolean
+ * @todo implement/test
+ */
+Entity.prototype.validate = function() {
 	var def = getDefinition(vz.definitions.entities, entity.type);
 	
 	def.required.each(function(index, property) {
@@ -123,6 +127,11 @@ Entity.prototype.validate = function(entity) {
 	return true;
 };
 
+/**
+ * Calls the callback function for the entity and all nested children
+ * 
+ * @param cb callback function
+ */
 Entity.prototype.each = function(cb, parent) {
 	cb(this, parent);
 	
diff --git a/frontend/javascripts/frontend.js b/frontend/javascripts/frontend.js
index 4e13e8a..9f1a5cb 100644
--- a/frontend/javascripts/frontend.js
+++ b/frontend/javascripts/frontend.js
@@ -119,7 +119,7 @@ vz.refresh = function() {
  */
 vz.handleControls = function () {
 	var delta = vz.to - vz.from;
-	var middle = Math.round(vz.from + delta/2);
+	var middle = vz.from + delta/2;
 	
 	switch(this.value) {
 		case 'move_last':
@@ -137,13 +137,13 @@ vz.handleControls = function () {
 			break;
 		
 		case 'zoom_reset':
-			vz.from = middle - Math.floor(defaultInterval/2);
-			vz.to =  middle + Math.ceil(defaultInterval/2);
+			vz.from = middle - efaultInterval/2;
+			vz.to =  middle + defaultInterval/2;
 			break;
 			
 		case 'zoom_in':
-			vz.from += Math.floor(delta/4);
-			vz.to -= Math.ceil(delta/4);
+			vz.from += delta/4;
+			vz.to -= delta/4;
 			break;
 			
 		case 'zoom_out':
@@ -215,12 +215,12 @@ vz.entities.show = function() {
 				.append($('<td>'))	// avg
 				.append($('<td>')	// operations
 					.addClass('ops')
-					.append($('<input>')
+					/*.append($('<input>')
 						.attr('type', 'image')
 						.attr('src', 'images/information.png')
 						.attr('alt', 'details')
 						.bind('click', entity, function(event) { event.data.showDetails(); })
-					)
+					)*/
 				);
 					
 			if (parent == null) {
@@ -250,14 +250,14 @@ vz.entities.show = function() {
 };
 
 /**
- * Load json data with given time window
+ * Load json data from the backend
  */
 vz.data.load = function() {
 	vz.data.clear();
 	vz.entities.each(function(index, entity) {
 		entity.each(function(entity, parent) {
 			if (entity.active && entity.type != 'group') {
-				$.getJSON(vz.options.backendUrl + '/data/' + entity.uuid + '.json', { from: vz.from, to: vz.to, tuples: vz.options.tuples }, ajaxWait(function(json) {
+				$.getJSON(vz.options.backendUrl + '/data/' + entity.uuid + '.json', { from: Math.floor(vz.from), to: Math.ceil(vz.to), tuples: vz.options.tuples }, ajaxWait(function(json) {
 					vz.data.push({
 						data: json.data[0].tuples,	// TODO check uuid
 						color: entity.color
@@ -268,6 +268,9 @@ vz.data.load = function() {
 	});
 };
 
+/**
+ * Draws plot to container
+ */
 vz.drawPlot = function () {
 	vz.options.plot.xaxis.min = vz.from;
 	vz.options.plot.xaxis.max = vz.to;
diff --git a/frontend/javascripts/init.js b/frontend/javascripts/init.js
index 3f77adc..23f3e55 100644
--- a/frontend/javascripts/init.js
+++ b/frontend/javascripts/init.js
@@ -107,6 +107,13 @@ $(document).ready(function() {
 		vz.uuids.add($.getUrlVar('uuid'));
 	}
 	
+	if (vz.uuids.length == 0) {
+		$('#addUUID').dialog({
+			title: 'UUID hinzufügen',
+			width: 400
+		});
+	}
+	
 	// start auto refresh timer
 	window.setInterval(vz.refresh, 5000);
 	
diff --git a/frontend/javascripts/property.js b/frontend/javascripts/property.js
index 9c7d029..c3474de 100644
--- a/frontend/javascripts/property.js
+++ b/frontend/javascripts/property.js
@@ -25,12 +25,18 @@
  */
 
 /**
- * Property
+ * Property constructor
  */
 var Property = function(key, value) {
 	
 };
 
+/**
+ * Validate value
+ * @param value
+ * @return boolean
+ * @todo implement/test
+ */
 Property.prototype.validate = function(value) {
 	switch (property.type) {
 		case 'string':
@@ -60,6 +66,10 @@ Property.prototype.validate = function(value) {
 	}
 };
 
+/**
+ * 
+ * @todo implement/test
+ */
 Property.prototype.getDOM = function() {
 	switch (property.type) {
 		case 'string':
diff --git a/frontend/javascripts/uuid.js b/frontend/javascripts/uuid.js
index ecd32bc..7b73834 100644
--- a/frontend/javascripts/uuid.js
+++ b/frontend/javascripts/uuid.js
@@ -24,8 +24,8 @@
  * volkszaehler.org. If not, see <http://www.gnu.org/licenses/>.
  */
 
-/*
- * Cookie & UUID related functions
+/**
+ * Read UUIDs from cookie and add them to the array
  */
 vz.uuids.parseCookie = function() {
 	if ($.getCookie('uuids')) {
@@ -35,6 +35,9 @@ vz.uuids.parseCookie = function() {
 	}
 };
 	
+/**
+ * Add given UUID and update cookie
+ */
 vz.uuids.add = function(uuid) {
 	if (vz.uuids.validate(uuid)) {
 		if (!vz.uuids.contains(uuid)) {
@@ -50,9 +53,13 @@ vz.uuids.add = function(uuid) {
 	}
 };
 	
+/**
+ * Remove UUID and update cookie
+ */
 vz.uuids.remove = function(uuid) {
+	console.log(vz.uuids.contains(uuid));
 	if (vz.uuids.contains(uuid)) {
-		vz.uuids.remove(uuid);
+		vz.uuids.splice(this.indexOf(uuid), 1);	// remove uuid from array
 		$.setCookie('uuids', JSON.stringify(vz.uuids));
 	}
 	else {
@@ -60,6 +67,9 @@ vz.uuids.remove = function(uuid) {
 	}
 };
 	
+/**
+ * Validate UUID
+ */
 vz.uuids.validate = function(uuid) {
 	return new Boolean(uuid.match(/^[0-9a-zA-Z]{8}-[0-9a-zA-Z]{4}-[0-9a-zA-Z]{4}-[0-9a-zA-Z]{4}-[0-9a-zA-Z]{12}$/));
 };
\ No newline at end of file