Bug 1837262 - Addendum SeaMonkey website for 2.53.17 beta 1 release. r=me

src/releases/seamonkey2.53.17/index.en.html

@@ -110,7 +110,6 @@ for new information.
   <li>Remove nsIPrefBranch2 and nsIPrefBranchInternal <a
     href="https://bugzilla.mozilla.org/show_bug.cgi?id=1374847">bug 1374847</a>.
   </li>
-  <li>Continue the switch from Python 2 to Python 3 in the build system.</li>
 </ul>
 <!--
 <p>
@@ -176,10 +175,8 @@ backported. We will continue to enhance SeaMonkey security in subsequent
 <h3>SeaMonkey-specific changes</h3>
 <ul>
   <li>SeaMonkey now uses gtk3 on Linux. If you experience a problem because of
-  this please file a bug and link it to <a
-  href="https://bugzilla.mozilla.org/show_bug.cgi?id=1367257">bug 1367257</a>.
-  Please try another OS theme first. Some of them are buggy and cause problems
-  with SeaMonkey, Thunderbird and Firefox.
+  this please file a bug. Please try another OS theme first. Some of them are
+  buggy and cause problems with SeaMonkey, Thunderbird and Firefox.
   </li>
 </ul>
 
@@ -241,16 +238,16 @@ note the following warnings and advice regarding extensions:</p>
   </li>
   <li>For <b>Enigmail</b>, please refer to the
     <a href="https://enigmail.net/index.php/en/home">Enigmail</a> page.
-    <br>The latest supported version is 2.0.9
-    <a href="https://www.enigmail.net/download/release/2.0/enigmail-2.0.9-sm+tb.xpi">
-    Enigmail</a> but there have been some problems reported against it.
+    <br>The latest supported version is 3.1.4
+    <a href="https://enigmail.net/download/release/3.1/enigmail-3.1.4-il.xpi">
+    Enigmail</a>.
   </li>
   <li>Adblock Plus 2.9.1 may cause huge memory and CPU consumption and is not
     recommended or officially supported in this SeaMonkey version. Consider
     switching to uBlock.
   </li>
-  <li>Lightbird 0.7.1. is not compatible with this version. The message preview
-    pane will not update itself correctly.
+  <li>Lightbird 0.7.1. is not compatible with this version. Until a fixed
+    version is released you need to uninstall it.
   </li>
   <li>The latest 1.16.x working version of uBlock can be found
     <a href="https://github.com/gorhill/uBlock-for-firefox-legacy/releases">here</a>.
@@ -259,12 +256,14 @@ note the following warnings and advice regarding extensions:</p>
   <li>The latest working version of NoScript Classic 5.x can be found
     <a href="https://noscript.net/getit">here</a>.
   </li>
-  <li>Lightweight themes are no longer provided on the SeaMonkey Add-ons site.
+  <li>Full theme add-ons are still fully supported but may need changes because
+    of user interface and internal changes. If you find any problem with themes,
+    contact the theme author. Before reporting a problem with the user interface
+    please make sure to recreate it with either the Classic or Modern theme.
   </li>
-  <li>Full theme add-ons may need changes because of user interface and internal
-    changes. If you find any problem with themes, contact the theme author.
-    Before reporting a problem with the user interface please make sure to
-    recreate it with either the Classic or Modern theme.
+  <li>Lightweight themes are no longer provided on the SeaMonkey Add-ons site
+    and installed existing themes might be broken. Support for web extension
+    themes will be added at a later date.
   </li>
   <li>Because of security backports which removed obsolete code, Session Manager
     add-on version 0.8.1.14 or above is required to be compatible with current
@@ -289,10 +288,6 @@ Please read this before reporting any new bugs.
     languages like Polish are now missing a translator. Consider helping out
     with translations if you would like to have a 100% translated version.
   </li>
-  <li>Opening single new tabs from the Library always loads them in the
-    foreground. The problem is tracked in <a
-    href="https://bugzilla.mozilla.org/show_bug.cgi?id=1619108">bug 1619108</a>
-  </li>
   <li>SeaMonkey will not start under Linux if you downloaded the wrong package.
     <br>We are providing x86 and x64 versions of SeaMonkey for Linux.
     For newer distributions you probably need the Linux x64 version.
@@ -417,7 +412,7 @@ Please read this before reporting any new bugs.
   </li>
   <li>In ChatZilla users are unable to add an exception for an invalid
     certificate unless an override is added to the preferences (see <a
-    href="https://bugzilla.mozilla.org/show_bug.cgi?id=1738597">bug 1738597</a>).
+    href="https://bugzilla.mozilla.org/show_bug.cgi?id=1720878">bug 1720878</a>).
   </li>
   <li>Linux:
     <ul>