doc: Fix HTTPS encryption.

wiki/src/doc/about/warning.mdwn

@@ -8,6 +8,8 @@ helping you making a good use of it.
 
 [[!toc levels=2]]
 
+<a id="exit_node"></a>
+
 Tor exit nodes can eavesdrop on communications
 ==============================================
 

wiki/src/doc/anonymous_internet/iceweasel.mdwn

@@ -14,12 +14,15 @@ Here are a few things worth mentioning in the context of Tails.
 HTTPS Encryption
 ================
 
-<!--
-Do you remember what we said earlier about end-to-end encryption and its
-importance while using Tor?
+Using HTTPS instead of HTTP encrypts your communication while browsing the web.
 
-**FIXME** link to documentation about end-to-end encryption
--->
+All the data exchanged between your browser and the server you are visiting are
+encrypted. It prevents the
+[[Tor exit node to eavesdrop on your communication|doc/about/warnings#exit_node]].
+
+HTTPS also includes mechanisms to authenticate the server you are communicating
+with. But those mechanisms can be flawed,
+[[as explained on our warning page|about/warning#man-in-the-middle]].
 
 For example, here is how the browser looks like when we try to log in an email
 account at [lavabit.com](http://lavabit.com/), using their [webmail