The role of a User Interface (UI) developer is to provide the user interface solution to the end user, including the final look, feel and behaviour of the interface in different contexts. They role of a UI Developer is the transformational combination of the roles of both the Web Designer and the Web Developer
The task of the Web Designer was to design and create a page without considering the functional aspects of the page. The page was then passed on to the Web Developer to add functionalities to it. But the changing nature of the industry and client requirements to have developers capable enough of adding dynamic content to web pages, lead to the evolution of the role of web designers into UI developers.
UI Developers see a website as a collection of assets applied to the pages and are concerned with the overall user experience. Their role is basically concerned with the following aspects of User experience:
Aesthetics (Look and feel) of the UI