diff --git a/src/Umbraco.Core/Constants-Web.cs b/src/Umbraco.Core/Constants-Web.cs
new file mode 100644
index 0000000000..83cb995eeb
--- /dev/null
+++ b/src/Umbraco.Core/Constants-Web.cs
@@ -0,0 +1,22 @@
+namespace Umbraco.Core
+{
+	public static partial class Constants
+	{		
+        /// <summary>
+        /// Defines the identifiers for Umbraco system nodes.
+        /// </summary>
+        public static class Web
+        {
+            /// <summary>
+            /// The preview cookie name
+            /// </summary>
+            public const string PreviewCookieName = "UMB_PREVIEW";
+
+            /// <summary>
+            /// The auth cookie name
+            /// </summary>
+            public const string AuthCookieName = "UMB_UCONTEXT";
+
+        }
+	}
+}
\ No newline at end of file
diff --git a/src/Umbraco.Core/Security/AuthenticationExtensions.cs b/src/Umbraco.Core/Security/AuthenticationExtensions.cs
index b642796932..6ba1df8b6c 100644
--- a/src/Umbraco.Core/Security/AuthenticationExtensions.cs
+++ b/src/Umbraco.Core/Security/AuthenticationExtensions.cs
@@ -259,21 +259,27 @@ namespace Umbraco.Core.Security
         private static void Logout(this HttpContextBase http, string cookieName)
         {
             if (http == null) throw new ArgumentNullException("http");
-            //remove from the request
-            http.Request.Cookies.Remove(cookieName);
+            //clear the preview cookie too
+            var cookies = new[] { cookieName, Constants.Web.PreviewCookieName };
+            foreach (var c in cookies)
+            {
+                //remove from the request
+                http.Request.Cookies.Remove(c);
+
+                //expire from the response
+                var formsCookie = http.Response.Cookies[c];
+                if (formsCookie != null)
+                {
+                    //this will expire immediately and be removed from the browser
+                    formsCookie.Expires = DateTime.Now.AddYears(-1);
+                }
+                else
+                {
+                    //ensure there's def an expired cookie
+                    http.Response.Cookies.Add(new HttpCookie(c) { Expires = DateTime.Now.AddYears(-1) });
+                }               
+            }            
 
-            //expire from the response
-            var formsCookie = http.Response.Cookies[cookieName];
-            if (formsCookie != null)
-            {
-                //this will expire immediately and be removed from the browser
-                formsCookie.Expires = DateTime.Now.AddYears(-1);
-            }
-            else
-            {
-                //ensure there's def an expired cookie
-                http.Response.Cookies.Add(new HttpCookie(cookieName) { Expires = DateTime.Now.AddYears(-1) });
-            }
         }
 
         private static FormsAuthenticationTicket GetAuthTicket(this HttpContextBase http, string cookieName)
diff --git a/src/Umbraco.Core/Umbraco.Core.csproj b/src/Umbraco.Core/Umbraco.Core.csproj
index 07d5d8f681..471eb1e28a 100644
--- a/src/Umbraco.Core/Umbraco.Core.csproj
+++ b/src/Umbraco.Core/Umbraco.Core.csproj
@@ -1061,6 +1061,9 @@
     <Compile Include="Constants-System.cs">
       <DependentUpon>Constants.cs</DependentUpon>
     </Compile>
+    <Compile Include="Constants-Web.cs">
+      <DependentUpon>Constants.cs</DependentUpon>
+    </Compile>
     <Compile Include="UpgradeableReadLock.cs" />
     <Compile Include="DelegateEqualityComparer.cs" />
     <Compile Include="Media\IEmbedProvider.cs" />
diff --git a/src/umbraco.businesslogic/StateHelper.cs b/src/umbraco.businesslogic/StateHelper.cs
index 10e81dd614..e84d3aa129 100644
--- a/src/umbraco.businesslogic/StateHelper.cs
+++ b/src/umbraco.businesslogic/StateHelper.cs
@@ -349,7 +349,7 @@ namespace umbraco.BusinessLogic
              * we currently reproduce this by configuring each cookie with a 30d expires, but does
              * that actually make sense? shouldn't some cookie have _no_ expires?
              */
-            static readonly Cookie _preview = new Cookie(Constants.Web.PreviewCookieName, 30d); // was "PreviewSet"
+            static readonly Cookie _preview = new Cookie(Constants.Web.PreviewCookieName, TimeSpan.Zero); // was "PreviewSet"
             static readonly Cookie _userContext = new Cookie(Constants.Web.AuthCookieName, 30d); // was "UserContext"
             static readonly Cookie _member = new Cookie("UMB_MEMBER", 30d); // was "umbracoMember"
 
@@ -431,7 +431,7 @@ namespace umbraco.BusinessLogic
                 }
                 public void SetValue(string value)
                 {
-                    SetValueWithDate(value, DateTime.Now + _expires);
+                    SetValueWithDate(value, _expires == TimeSpan.Zero ? DateTime.MinValue : DateTime.Now + _expires);
                 }
 
                 public void SetValue(string value, double days)
@@ -441,7 +441,7 @@ namespace umbraco.BusinessLogic
 
                 public void SetValue(string value, TimeSpan expires)
                 {
-                    SetValue(value, DateTime.Now + expires);
+                    SetValue(value, expires == TimeSpan.Zero ? DateTime.MinValue : DateTime.Now + expires);
                 }
 
                 public void SetValue(string value, DateTime expires)
@@ -451,7 +451,7 @@ namespace umbraco.BusinessLogic
 
                 private void SetValueWithDate(string value, DateTime expires)
                 {
-                    HttpCookie cookie = new HttpCookie(_key, value);
+                    var cookie = new HttpCookie(_key, value);
 
                     if (GlobalSettings.UseSSL)
                         cookie.Secure = true;
@@ -459,7 +459,12 @@ namespace umbraco.BusinessLogic
                     //ensure http only, this should only be able to be accessed via the server
                     cookie.HttpOnly = true;
 
-                    cookie.Expires = expires;
+                    //set an expiry date if not min value, otherwise leave it as a session cookie.
+                    if (expires != DateTime.MinValue)
+                    {
+                        cookie.Expires = expires;    
+                    }
+                    
                     ResponseCookie = cookie;
 
                     // original Umbraco code also does this
@@ -473,7 +478,7 @@ namespace umbraco.BusinessLogic
                 {
                     if (RequestCookie != null || ResponseCookie != null)
                     {
-                        HttpCookie cookie = new HttpCookie(_key);
+                        var cookie = new HttpCookie(_key);
                         cookie.Expires = DateTime.Now.AddDays(-1);
                         ResponseCookie = cookie;
                     }