It's incorrect English in many places. Right on the landing page, for instance:
Replace them with a real live preview feature to help you concentrate the content itself
If you don't know what's missing from that sentence [hint: it's a missing preposition], you are probably not a native English speaker. There are numerous other examples. It's important that apps like this have good English copy.
I think the author speaks better English than you, or, at least, types it.