title: what is really the difference and advantage using bootstrap.css and bootstrap-responsive.css
body: <p>I m designing responsive web page layout suing <code>bootstrap 3.x.x</code> and i see that grid design is supported  in <code>bootstrap.css</code> and <code>bootstarp-responsive.css</code> , when i  look my code after render on browser , i see that responsive css override the one default css of bootstrap.</p>
  
  <p>And , i would like to know what can do about it , </p>
  
  <p>1.Do you really need to add <code>bootstarp-responsive.css</code> when ever u use bootstrap page and what is exactly the diffrence it will make ?</p>