> That's only half the answer. The real answer is that no one wants to spend the time to offer those features securely.

>It's perfectly cromulent to allow users to upload CSS and html and even javascript. You just have to put a lot of effort into making it safe.

I work in an online payment company. Custom CSS is one of the features we hate the most implementing. It is very difficult to get it right and the cost of maintenance is quite high.