Overflow hidden doesn't work on firefox

[admin]

Yesterday i check that one highlights products slide that i have in the home of one webpage is not property vertical aligned only on firefox, it works fine on IE and Chrome.

I was searching info and i find a lot of many years ago bugs on FF. I try a few solutions i find but no one works.

<div id="feature-wrap-container">
    <div id="feature_wrap">
        <div id="scrollable">
           //a list of element floating left
        </div>
    </div>
</div>

#feature-wrap-container{
 background-color: #ffffff;
 width: 100%;
 height: 260px;
}

#feature_wrap {
 width: 960px;
 height: 260px;
 overflow:hidden;
 position: relative;
 left: 0;
 right: 0;
 margin-left: auto;
 margin-right: auto;
}

#scrollable {
 height:100%;
}

On chrome and IE the div is center on the window and in firefox the feature_wrap align to right and make the window bigger than the 100%.

The slide is based on: <a href="http://wordpress.org/extend/plugins/featured-posts-slideshow/" rel="nofollow">http://wordpress.org/extend/plugins/featured-posts-slideshow/</a>, but obviously modified.

Thanks in advance.