Best way to design UI for java webapps

I understand that there are lots of web frameworks available for developing UI of java web applications. But I am not that good at designing UI; so I require a framework which gives me a UI designer as well. Is there any utility/tool/framework/eclipse-plugi开发者_开发技巧n which lets me design a good UI?

Google plugin might help - http://code.google.com/eclipse/