Document blank page in GUI

#66

content/guidelines/declaring.en.md

@@ -192,3 +192,17 @@ You can only use our copyrights or [trademarks (or any similar marks)](https://l
 #### Solution
 
 Write a filter in the declaration.
+
+- - -
+
+## Using the graphical contribution interface
+
+### Blank page when contacting support
+
+While using the graphical user interface for contribution, you may come across a blank page when trying to contact the team.
+
+This may be caused by the lack of a mail program being set up in your browser.
+
+#### Solution
+
+If you use Gmail, for example, [these instructions](https://support.google.com/chrome/thread/57026170/how-to-add-gmail-as-default-mailto-handler) explain how to add Gmail as the default `mailto` handler in Chrome. Try following them and trying again.