My example above was possibly too simplistic. I'm not using Enlive at the moment but am merely trying to gauge what kinds of contracts would allow the developers and designers work together most efficiently. I can imagine a fairly big difference between, for example, the following two contracts:

a) "Don't touch the markup without an explicit agreement between the two of us."

b) "Please make sure you have an element with a data-content-for='user.username' somewhere in the HTML."