Wolfram MathWorld is an online math encyclopedia. All its content is approved by an chief editor (Eric Weissman). They accept contributions from the general public, but they don't have a free-wheeling wiki as do other online projects such as Conservapedia and Wikipedia.
The website content is freely available and run pro bono by Stephen Wolfram's company, Wolfram Research.
Their anti-spam question was:
- Wolfram MathWorld - "the Web's Most Extensive Mathematics Resource".