I would guess that your spring MVC config is set to handle something like /*. So a request comes in for your stylesheet and it'll complain because it hasn't got a controller that matches this URL pattern. What you need is a way to tell spring which URL's are for static resources.
Try adding something like this to your MVC config.
<mvc:resources mapping="/resources/**" location="/resources/" />
For the above config to work you'd have to move all your static files into a folder called resources. You could name it something else.
Have a read of the docs for more info:
http://docs.spring.io/spring/docs/3.1.x/spring-framework-reference/html/mvc.html
You want 16.14.5
... oh yes and move them into src/main/webapp!