We use this domain to render code snippets from documentations. Interactive content like css and javascript can be added so users can see the output without going to another site. We host the results on a different domain because we must prevent same-origin from being in effect. If same-origin was possible, users could write code that caused other users to do things that they didn't want to on their Dilif account. What kinds of things? Evil things. Things like logging a user out, or updating their profile, or even possibly posting on their behalf! So, this domain stops bad people from doing bad things.