diff --git a/How-to-whitelist-a-web-site.md b/How-to-whitelist-a-web-site.md
index 32fce42..3d0bab8 100644
--- a/How-to-whitelist-a-web-site.md
+++ b/How-to-whitelist-a-web-site.md
@@ -12,10 +12,12 @@ As of version 0.8.2.0, the whitelist directive syntax is split into two classes:
 - Plain
 - Complex
 
-Plain syntax is when using only hostname label(s), which means only the hostname portion of a URL will be taken into account.
+Plain syntax is when using only hostname label(s), which means only the hostname portion of a URL will be taken into account. With plain syntax, the matching is performed by comparing the right-most portion of the page hostname with the whitelist directive. Wildcards are not allowed when using plain syntax.
 
 Complex syntax occurs if and only if at least one `/` appears in a whitelist directive. Optionally, wildcard `*` can be used with complex directives for more flexibility.
 
+If no `/` appears in a whitelist directive, and if the directive contains characters which are not allowed for plain hostname, then the whitelist directive will be commented out and ignored by µBlock.
+
 #### Plain hostname
 
 - `example.com`: whitelist all pages from `example.com` or above (i.e. `example.com`, `www.example.com`).