Visual Presentation Skills
A picture might be worth more than 1000 words when putting together a Web site. Even if the Web site works properly, graphical enhancements and layouts attract new users and give a professional appearance to the site. Depending on what's being presented, many different skills are needed. The minimal skill set is HTML.
HTML development doesn't require the same technical expertise as coding in Java, but it isn't necessarily easy. J2EE applications have both dynamic and static pages. The dynamic pages are written in JSP and servlet format, whereas the static pages are plain HTML.
It's also necessary to point out that senior Java developers could have adequate skills for HTML and design, which is helpful. But in my experience, they don't necessarily create the most attractive sites using and watching out for any nuances the way a dedicated HTML person would.
Graphical user interface design is the key component to application usability. Most of the time, the designs change several times before a product is released. The actual programmers sometimes work with the users to find the screen layouts and functionality. This isn't always the best idea. Users are normally used to the old way they did things, so instead of improving the process or using a new layout that might be easier, they want exactly what they had before.
A better choice is to use a GUI designer who understands these concepts and components. Bigger application companies employ designers for this reason. Sometimes it's not feasible to hire one because of budget constraints. In that case, the developers must be trained in GUI development. Good GUI design can make or break an application because the GUI is what the customer sees first. The customer won't see all the work that was put into the back end of an application, and applaud you for that design, until he can easily learn, find, and use the application's front end.
The days of presenting green screens full of data are gone. The presentation of data is now expected to please the senses. In a WLS format, not only must data be created, but pictures, movies, sounds, and other multimedia must also be created and distributed. Engineers don't usually have the skills to create and manipulate this art (they're too busy reading technical manuals). A graphic artist is now becoming a must in the development of applications. The graphic artist works with the GUI designer to create visually appealing screens. The skill of the graphic artist obviously depends on the applications you're building. The more visually intensive your applications are, the better the artist must be.