What happens upon reaching account limits?

I hope to justify going from a free starter form to the next level. But until I can, what will happen when someone is using the form, but their submission runs up against one of my limiting categories, like number of submissions or storage space? What will the submitting customer experience?

You will be informed if you come close to the limit and over the limit. The forms on the over-limit accounts are being temporarily disabled. The following page is displayed instead of the actual forms when the users access them.