You must be at least 17 years old to download this app.
Frequent/Intense Sexual Content or Nudity
Frequent/Intense Profanity or Crude Humor
Frequent/Intense Mature/Suggestive Themes
Frequent/Intense Cartoon or Fantasy Violence
Frequent/Intense Horror/Fear Themes
Frequent/Intense Realistic Violence
Frequent/Intense Alcohol, Tobacco, or Drug Use or References
update: did you actually look at the picture that you linked? I doubt a 14 year old is going to be harmed by it...
I did look at the picture, and intentionally picked it for humor and inclusion in my permanent HN comment history. I don't think any 4+ year old would be harmed at it, but I also think the parents of many 4+ year olds wouldn't want them bandying it about, especially in very religious communities.
Any app that allows general web access must be given a 17+ rating. This includes any browser, as well as any app that happens to include an integrated browser for another purpose (e.g. a Twitter client that shows links in-app).
As for children having access to the built-in web browser, certainly not if their parents don't think full web access is appropriate for them.