CSS div(position relative) ignores another div(position: absolute) - html

Question

Trying to build a site with a fixed, non-scrolling header area (called "top_box") and a scrollable content area (called "middle_box").
The top_box is position: absolute.
The middle_box is position: relative.
The middle_box is "ignoring" the top_box and is displayed across the top_box, instead of being displayed beneath it.
#top_box {
position: fixed !important;
position: absolute;
top: 2%;
height: 20%;
}
#middle_box {
position: relative;
height: 70%;
overflow: auto;
}
<div id="top_box">
...
</div>
<div id="middle_box">
...
</div>
Any ideas why middle_box ignores top_box and starts on the top of the screen instead of starting beneath top_box?

Answer 1

The problem is that position: fixed or position:absolute takes the div out of the flow. Because of that your relative div won't notice that there is already one above. So it will be placed at the top.
To achieve what you want you have to change your CSS to the following.
I've set the content, in your case the div #middle_box to the height: 1000px so you can see that the content area is scrollable and your other div #top_box stays on top.
body {
margin: 0;
}
#top_box {
position: fixed;
top: 0;
left: 0;
width: 100%;
height: 20%;
background: #eee;
z-index: 100;
}
#middle_box {
position: absolute;
top: 20%;
left: 0;
width: 100%;
height: 1000px;
background: rgba(0, 0, 0, 0.3);
}
<div id="top_box">
top_box
</div>
<div id="middle_box">
middle_box
</div>

Answer 2

Why you have to give position:relative to the second box?
#top_box {
position: absolute;
top: 2%;
height: 20%;
background:red;
}
#middle_box {
position: absolute;
top:20%;
height: 70%;
background:blue;
}
<div id="top_box">
TOP
</div>
<div id="middle_box">
BOTTOM
</div>

Answer 3

#top_box{
position: fixed;
top: 2%;
height: 20%;
overflow: hidden;
}
#middle_box
{
position: fixed;
top: 22%; /* this should set to 22%-30% depending at where do you want it*/
height: 70%;
overflow: auto;
}

Answer 4

fixed !important; would prevail over absolute
also beneath it wouldn't be, since it will start within the parent, not below it
#top_box {
position: absolute;
top: 2%;
height: 20%;
background-color: yellow;
}
#middle_box {
position: relative;
height: 70%;
overflow: auto;
background-color: blue;
}
<div id="top_box">
Lorem Ipsum 1
</div>
<div id="middle_box">
Lorem Ipsum 2
</div>

Answer 5

I don't know what actually u mean about scrollable content area . I think you mean it's a scrolling section when there is overflow content. If that scrollable content meants that you want a overflow scrolling. You can make this without using position. I change the middle box % to px so that scroll when overflowing content. Any Question ask me in comment thanks.
#top_box {
text-align: center;
height: 20%;
border: 1px solid blue;
}
#middle_box {
overflow: auto;
height: 280px; /*change the height otherwise 70% will never scroll that content*/
background: red;
border: 1px solid black;
color: white;
text-align: justify;
padding:0 10px;
}
h1.tittle {
text-align: center;
}
#footer_box {
border: 1px solid yellow;
text-align: center;
}
<div id="top_box">
<h1>
Non-scroll Top Header area
</h1>
</div>
<div id="middle_box">
<h1 class="tittle">
Scrolling Header
</h1> Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It
has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop
publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer
took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset
sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum. Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's
standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.
It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing
and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the
leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including
versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a
type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more
recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,
when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with
the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem
Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting,
remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum
is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived
not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software
like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of
type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing
Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy
text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised
in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting
industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic
typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem
Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived
not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software
like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of
type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing
Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
</div>
<div id="footer_box">
<h1>Footer area</h1>
</div>