update documentation on web hooks by suggestion [ci skip]

doc/web_hooks/web_hooks.md

@@ -8,7 +8,10 @@ Web hooks can be used to update an external issue tracker, trigger CI builds, up
 
 ## SSL Verification
 
-Web hooks do SSL verification by default.
+By default, the SSL certificate of the webhook endpoint is verified based on 
+an internal list of Certificate Authorities, 
+which means the certificate cannot be self-signed.
+
 You can turn this off in the web hook settings in your GitLab projects.
 
 ![SSL Verification](ssl.png)
@@ -534,4 +537,4 @@ When you press 'Test Hook' in GitLab, you should see something like this in the
 {"before":"077a85dd266e6f3573ef7e9ef8ce3343ad659c4e","after":"95cd4a99e93bc4bbabacfa2cd10e6725b1403c60",<SNIP>}
 example.com - - [14/May/2014:07:45:26 EDT] "POST / HTTP/1.1" 200 0
 - -> /
-```
+```
\ No newline at end of file