rails3 form_for adding element class...because...?

When I use a form_for, it's adding an element class attribute on the form, which is mucking up the design. After some digging, I came upon this thread:


Which appears to indicate that the class attribute is defined in the routes file. I don't have any routes associated with this controller in my routes, so I guess it's just adding a default value.

How can I make this not happen? And if anybody would like to explain why it's happening, I'd like to understand that. I am at a loss as to how this could be considered a good idea.