Color gradient not working in Firefox - css

Question

Ok my problem is that in firefox my hover gradient is showing up as black to white. Black being the top color and white as the bottom. Here is the css hover code I'm using. It doesn't make sense to me because I'm not even using the color codes for black or white. Any help would be greatly appreciated!
nav a {
color: #fff;
background: #b9b9b9; /* Old browsers */
background: -moz-linear-gradient(top, #b9b9b9 0%, #616161 99%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#b9b9b9), color-stop(99%,#616161)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #b9b9b9 0%,#616161 99%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, #b9b9b9 0%,#616161 99%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #b9b9b9 0%,#616161 99%); /* IE10+ */
nav a:hover, nav a:active {
background: #b9b9b9; /* Old browsers */
background: -moz-linear-gradient(bottom, #4f4f4f, #b9b9b9 ); /* FF3.6+ */
background: -webkit-linear-gradient(top, #b9b9b9 0%,#4f4f4f 99%); /*
background: -o-linear-gradient(top, #b9b9b9 0%,#4f4f4f 99%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #b9b9b9 0%,#4f4f4f 99%); /* IE10+ */
background: linear-gradient(to bottom, #b9b9b9 0%,#4f4f4f 99%); /* W3C */

Answer 1

You are missing your closing braces.
Your code works otherwise: http://jsfiddle.net/66QQV/
nav a
{
color: #fff;
background: #b9b9b9; /* Old browsers */
background: -moz-linear-gradient(top, #b9b9b9 0%, #616161 99%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#b9b9b9), color-stop(99%,#616161)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #b9b9b9 0%,#616161 99%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, #b9b9b9 0%,#616161 99%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #b9b9b9 0%,#616161 99%); /* IE10+ */
}
nav a:hover, nav a:active
{
background: #b9b9b9; /* Old browsers */
background: -moz-linear-gradient(bottom, #4f4f4f, #b9b9b9 ); /* FF3.6+ */
background: -webkit-linear-gradient(top, #b9b9b9 0%,#4f4f4f 99%); /*
background: -o-linear-gradient(top, #b9b9b9 0%,#4f4f4f 99%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #b9b9b9 0%,#4f4f4f 99%); /* IE10+ */
background: linear-gradient(to bottom, #b9b9b9 0%,#4f4f4f 99%); /* W3C */
}
This is assuming that you intend to put an <a> element inside of a <nav> element ... if you meant for this to be a class or an ID (such as <span class="nav"> or <div id="nav">), you need to use .nav or #nav instead, respectively.