There's a lot of porn on Tumblr. Over a fifth of content on the site (disclaimer: it's a sister brand through Verizon's Yahoo purchase) is adults-only, if you ask the analytics firm SimilarWeb. And that's a problem if you're surfing from work or giving access to your kids, since there's a real chance you could see some naughtiness. Tumblr is ready to help out beyond its existing filtering options, though. It's introducing a safe mode to its mobile and web apps that hides sensitive material from view. You can still click to see the content if you're over 18, but it won't be visible right away. Also, Tumblr is keen to add that this includes all "sensitive" material, not just naked bodies.