I am using (htmlLoad "mission_folder_1/mission_folder_2/miss_addon.html") in my mission to show a webpage with links to players when they are missing addons. It worked back in september 2015 but not anymore.
I don't have time to create a editor "purified" test mission for now. Will try do it if it's necessary.
Also, in the same mission it DOES work only if I use an URL like "http://www.bistudio.com/newsfeed/arma3_news.php?build=main&language=English"