Just coming to this late, but in case anyone else runs across this in the future, here’s your fix.
Your CSS Code:
.wrapper {
width:100%;
position:fixed;
z-index:10;
background:inherit;
}
.bottom-wrapper {
width:100%;
padding-top:92px;
z-index:5;
overflow:auto;
}
Your HTML:
<div class="wrapper">
...your header here...
</div>
<div class="bottom-wrapper">
...your main content here...
</div>
This will provide you with a header that cleanly matches your site, and floats at the top. The main content will scroll free of the header, and disappear when it passes the header.
Your .bottom-wrapper padding-top should be the height of your header wrapper’s content.
Cheers!