Z-index positioning not working properly - html

Question

I have a container I want to make a h2 appear aligned to the center with a slight line behind it. What I can't do is to make the line go behind the h2 box. No matter what I try, it keeps crossing over the h2 box.
Here goes a sample of what I need to accomplish:
Any help appreciated.
<div class="wrapper">
<div class="section-header">
<h2>H2 needs to be centered</h2>
<div class="line-section-header"></div>
</div>
</div>
The css I'm using is:
h2 {
font-family: 'Open Sans', Arial, sans-serif;
font-family: 20px;
font-weight: 700;
text-transform: uppercase;
width: 140px;
color: #3F3F3F;
background-color: white;
padding: 5px 10px;
border: 1px solid #D3D3D3;
text-align: center;
margin: 0 auto;
z-index: 999;
}
.wrapper {
margin: 0 auto;
width: 980px;
height: 1000px;
background-color: #white;
}
.section-header {
width: 100%;
height: auto;
background-color: white;
float: left;
position: relative;
}
.line-section-header {
width: 100%;
height: 1px;
background-color: #D3D3D3;
margin-top: 15px;
position: absolute;
}

Answer 1

I made a sample. check my jsfiddle http://jsfiddle.net/amitv1093/r3arp2m8/
html
<div class="container">
<h2> h2 </h2>
<div class="line"> </div>
</div>
css
.container
{
position:relative;
text-align:center;
background:#d9d9d9;
z-index:-99;
padding:12px 0px;
}
h2
{
width:100px;
background:grey;
height:50px;
text-align:center;
margin:0px auto;
line-height:50px;
}
.line
{
position:absolute;
width:100%;
height: 1px;
background: red;
top:50%;
margin:1px 0px;
z-index:-9;
}

Answer 2

h2 { //other props position: relative; }

Answer 3

alignment will be dynamic as container height
.wrapper {
margin: 0 auto;
width: 980px;
height: 1000px;
background-color: #white;
}
.section-header {
width: 100%;
height: auto;
background-color: white;
float: left;
position: relative;
}
h2 {
font-family: 'Open Sans', Arial, sans-serif;
font-family: 20px;
font-weight: 700;
text-transform: uppercase;
width: 140px;
color: #3F3F3F;
background-color: white;
padding: 5px 10px;
border: 1px solid #D3D3D3;
text-align: center;
margin: 0 auto;
z-index: 999;
position: relative;
}
.line-section-header {
width: 100%;
height: 1px;
background-color: #D3D3D3;
top: 50%;
position: absolute;
z-index: 1;
}
<div class="wrapper">
<div class="section-header">
<h2>H2 needs to be centered</h2>
<div class="line-section-header"></div>
</div>
</div>

Answer 4

Try adding this:
h2 {
position: absolute;
left:0;
right:0;
margin:auto;
}
.line-section-header {
margin-top: 50px;
position: absolute;
}

Answer 5

Try changing this in css:
h2 {
font-family: 'Open Sans', Arial, sans-serif;
font-family: 20px;
font-weight: 700;
text-transform: uppercase;
width: 140px;
color: #3F3F3F;
background-color: white;
padding: 5px 10px;
border: 1px solid #D3D3D3;
text-align: center;
margin: 0 auto;
margin-left: 420px;
z-index: 2;
position: absolute;
}
.wrapper {
margin: 0 auto;
width: 980px;
height: 1000px;
background-color: #white;
position: relative;
}
.section-header {
width: 100%;
height: auto;
background-color: white;
float: left;
position: relative;
}
.line-section-header {
width: 100%;
height: 1px;
background-color: #D3D3D3;
margin-top: 70px;
position: absolute;
z-index: 1;
}