Linked to #576 add validations styles

[smaimon]

Sending data on page creation is not enough. We also need to make sure that the data users fill out in forms is in the correct format that we need to process it successfully, and that it won't break Respond or when content appears on the Internet in more than one place.
e.g. what effect does create a page that already exist have on Respond?
We already now duplicated content is bad for SEO.
So adding some red messages like "This field is required" seems to be relevant.