I'm working on a website and the client is asking for raised-looking textboxes to match the look of the rest of the site. However, this makes the textboxes look like buttons that could potentially confuse new users. Here's an example from the signup modal.
In my experience, textboxes should have either a sunken look, or just a border or different background color in the case of flat design. This site is mostly-flat, where only modals, buttons, and textboxes look raised using a bottom-shadow. My gut says this is confusing and that textboxes should be flat.
I can't think of a single site that uses raised textboxes. But that's not a strong enough argument. Is there any supporting evidence that this UI is confusing? Or am I looking to much into this?