Contract should have Definitions of the Terms. On the one hand, you can't let the contract destroy the deal. On the other hand, a vaguely worded contract can poison the deal once it has transpired. Know what resources you will have to expend from the outset. From the moment you create original expression, you are creating copyrighted work.
Employer owns copyrights when worker creates within the scope of agreed upon employment.
It's called Work for Hire. Unless there is a contractual provision stating that the client owns the copyright, the web developer owns the copyright. The author of the work owns the copyright. Client will have implied license to use the work. If the client hasn't made them, the license can be terminated.