Hi This does not sound like an issue to do with Firefox for Android, but I will try my best to help. Safe Search is a options that is available from some search providers like Google, Bing and Yahoo. On their web pages, either at the top right or towards the bottom of a search results page, you should see an "cog" icon that will allow you to modify search settings, including Safe Search, I hope this helps, but if not, please come back here and we can look into a different solution for you.