Here’s a simple basic html/css (not bootstrap) fixed header with a max-width centered inline with the layout.

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<style>
html {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -ms-box-sizing: border-box;
    box-sizing: border-box;
}
*, *:before, *:after {
    -moz-box-sizing: inherit;
    -webkit-box-sizing: inherit;
    -ms-box-sizing: inherit;
    box-sizing: inherit;
}
html, body {
    margin:0;
    padding:0;
}
.header {
    position:fixed;
    left:0;
    right:0;
    width:1000px;
    max-width:1000px;
    height:100px;
    background:red;
    margin:auto;
}
@media screen and (max-width:1000px) {
.header {
    width:auto
}
}
.wrap {
    max-width:1000px;
    margin:auto;
    border:1px solid #000;
    padding:110px 10px 10px;
    background:#f9f9f9;
}
</style>

<!--[if lt IE 9]>
<style>
.header{width:auto}
</style>
<![endif]-->

</head>

<body>
<div class="header"> This is the fixed  header</div>
<div class="wrap">
        <p>Content starts here</p>
        <p>test</p>
        <p>test</p>
        <p>test</p>
        <p>test</p>
        <p>test</p>
        <p>test</p>
        <p>test</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
        <p>test scroll</p>
</div>
</body>
</html>