Design is not about how it looks. It is about how it works.
It is general misconception that people think about design just only as visual design.
Few years ago it was programmer's pain in the ass to make beautiful website without help of graphical designer. Not only because programmers usually do not know how to create graphical design. But also because it was not so easy to implement it in HTML + CSS.
But times has changed. Now it is really easy for every programmer who knows HTML + CSS to create nice looking, responsive website which works in all modern browsers.
Enter Bootstrap (formerly Twitter Bootstrap).
According to it's own definition, bootstrap is Sleek, intuitive, and powerful mobile first front-end framework for faster and easier web development.
And you can bet that it is!
Now you can design you application on the paper by creating sketches (remember, it is how it works!). Then after validation of your sketches you can create wireframes directly as HTML pages with bootstrap. All components like forms, buttons, navigation, toolbars and much much more are already there. You barely need to write your own CSS. Almost all the time it is possible to use just correct CSS classes for your elements.
You can just work on your website and you do not need to care how it will look on other browser. Bootstrap is well tested and supports all modern browsers.
You can focus on programming and not lose time with HTML and CSS. You can bootstrap your application design and focus on important things.
And later if it is necessary you can find some designer to help you change feel and look of you application. And you can still stay with bootstrap, because it is highly customizable. Just check all these beautiful websites based on it.