Add a drop shadow to a top-fixed nav bar using Bootstrap

In your css add the following to your .navbar class rule

.navbar {
    -webkit-box-shadow: 0 8px 6px -6px #999;
    -moz-box-shadow: 0 8px 6px -6px #999;
    box-shadow: 0 8px 6px -6px #999;

    /* the rest of your styling */
}

EDIT

There is an awesome online tool to generate box shadow code (thanks to the folks at cssmatic.com). You can adjust the way your shadow looks and it will generate all the code needed plus any specific browser prefixes (webkit, mozilla, etc.). You then can copy the code into your css.

http://www.cssmatic.com/box-shadow

You can also find other css effects in the same site.