It’s not entirely clear what you are looking for from your question, but if you are looking for something that can help you develop web applications with your interface, I would recommend looking at the front-end framework , for example twitter self-tuning .
The front-end interface is a structure of html, css and javascript, which simplifies the creation of web application interfaces. There's a little learning curve there, but once you get it, the advantage of having a predefined way to create layouts and a large set of reusable components is incredibly useful. We use it with ASP.NET MVC.
You still need to have some css skills to create custom sites for customers. However, there are sites that provide very professional downloadable themes, for example wrapbootstrap.com (see also bootswatch.com for some simple free examples.)
There are also sites that allow rapid prototyping using download components such as jetstrap.com , easel.io and divshot.com .
(Please note that a full download of these front-end platforms is available now. I have heard good things about the Fund. However, just leaving the net volume of questions on stackoverflow, bootstrap will prove to be the most popular nowadays. It is very actively developing.)