twitter-bootstrap – twitter引导程序在滚动后修复导航栏

我有一个导航栏,在加载时从页面顶部开始大约200px.当我向下滚动时,我希望导航栏能够“粘贴”到页面的顶部,并在滚动浏览其余内容时可见.
我可以让导航栏从顶部保持200px的位置,它忽略了我向右拉的内容并将其全部拉到左侧.我需要确保导航栏仍然可见,并且布局/样式在整个过程中都是相同的.

下面是我的jsfiddle,它显示了我遇到的麻烦

<!-- Begin logo / Search -->
  <header class="masthead">
      <div class="row">
        <div class="span6">
          <div class="logo pull-left">
              <h1><a href="/">name</a></h1>
          </div>
        </div>
        <div class="span6">
            <div class="pull-right hidden-phone">
                <form class="search" action="/search" id="site-search">
                    <input type="hidden" name="records" value="6">
                    <div class="input-append">
                        <input type="text" name="q" class="search_Box" placeholder="Search" value="" autocomplete="off" />
                        <button class="btn" type="submit"><i class="icon-search"></i></button>
                    </div>
                </form>     
            </div>
        </div>
      </div>
  </header>         


  <!-- Begin Navbar -->
  <div>
    <div class="navbar navbar-static">
      <div class="navbar-inner" id="mastnav">
        <div class="container">
            <!-- .btn-navbar is used as the toggle for collapsed navbar content -->
                <a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </a>
            <div class="nav-collapse collapse">
                <ul class="nav"><li><a href="#">nav</a> </li></ul>
                <ul class="nav pull-right">
                    <li>
                        <a href="/cart"><i class="icon-shopping-cart"></i> <span id="cart-count">1</span></a>
                    </li>
                </ul>
            </div>      
        </div>
      </div>
    </div><!-- /.navbar -->
  </div>

JSFIDDLE

#nav.affix {
    position: fixed;
    top: 0;
    width: 100%
}