如何在创建引导响应布局时设置容器div的宽度？

I am trying to make a bootstrap responsive layout. Here What I am trying is to short the width of the main container div. I tried setting width inline, but the layout lost its responsive nature. When I checked the bootstrap.css, the width for the container div is given auto. I would really appreciate if anyone can reveal the logic behind this. Following is the demo code of bootstrap. I am trying to make a bootstrap responsive layo