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Row submenu appears in wrong place after click [duplicate]

This question already has answers here:
Position absolute but relative to parent
(5 answers)
Closed 2 years ago.
I have static top bar and left menu, and scrollable long content on right. In my (long) submenu I use position: absolute to not change row height. Submenu position for rows 2 and 3 in below snippet is wrong and non-intuitive and unwanted scroll bar appear. How to fix it?
body { margin: 0}
button { height: 20px}
.hide { display:none; }
.container { display: flex; }
.topBar { background: red; height: 30px; }
.side__menu {
height: calc(100vh - 30px);
background: yellow;
display: flex;
flex-direction: column;
justify-content: space-between;
width:100px;
}
.main__panel {
overflow: auto;
height: calc(100vh - 30px);
width: calc(100vw - 100px);
}
.row {
display: flex;
justify-content: space-between;
align-items: center;
height: 200px;
background: #ddd;
margin: 10px;
}
.submenu {
position: absolute;
right: 100px;
background: #fdd;
height: 70px;
}
<div class="topBar">Top Bar</div>
<div class="container">
<div class="side__menu">
<div>item1</div><div>item2</div><div>menu footer</div>
</div>
<div class="main__panel">
<div class="row">
Row 1
<button onclick="s1.classList.toggle('hide')">toggle submenu</button>
<div id="s1" class="submenu hide">submenu</div>
</div>
<div class="row">
Row 2
<button onclick="s2.classList.toggle('hide')">toggle submenu</button>
<div id="s2" class="submenu hide">submenu</div>
</div>
<div class="row">
Row 3
<button onclick="s3.classList.toggle('hide')">toggle submenu</button>
<div id="s3" class="submenu hide">submenu</div>
</div>
</div>
</div>

I make some investigation and discover that height: 100vh (with calc or not) "create problems" with submenu. I accidentally find one solution - just add following style to row class
position: relative;
But I totally don't know why it actually works - so feel free to create answer and explain it if you know why (or show some alternative approach)
body { margin: 0}
button { height: 20px}
.hide { display:none; }
.container { display: flex; }
.topBar { background: red; height: 30px; }
.side__menu {
height: calc(100vh - 30px);
background: yellow;
display: flex;
flex-direction: column;
justify-content: space-between;
width:100px;
}
.main__panel {
overflow: auto;
height: calc(100vh - 30px);
width: calc(100vw - 100px);
}
.row {
display: flex;
justify-content: space-between;
align-items: center;
height: 200px;
background: #ddd;
margin: 10px;
position: relative;
}
.submenu {
position: absolute;
right: 100px;
background: #fdd;
height: 70px;
}
<div class="topBar">Top Bar</div>
<div class="container">
<div class="side__menu">
<div>item1</div><div>item2</div><div>menu footer</div>
</div>
<div class="main__panel">
<div class="row">
Row 1
<button onclick="s1.classList.toggle('hide')">toggle submenu</button>
<div id="s1" class="submenu hide">submenu</div>
</div>
<div class="row">
Row 2
<button onclick="s2.classList.toggle('hide')">toggle submenu</button>
<div id="s2" class="submenu hide">submenu</div>
</div>
<div class="row">
Row 3
<button onclick="s3.classList.toggle('hide')">toggle submenu</button>
<div id="s3" class="submenu hide">submenu</div>
</div>
</div>
</div>
Tested on: Chrome, Safari and Firefox

positioning div after it has been rotated

I would like to make a div with 3 texts, rotate it and place it on a fixed spot on the page. I would like it to perfectly fit the size of the screen,
So I created a div which height and width were the opposite of what I need then I rotated it. The thing is that I'm having problems positioning it correctly on the spot I want. (top:0 right:40px)
This is my code where I tried to move the div around.
.page {
width: 100%;
heigth: 100%;
background-color: #fefefe;
}
.green-band {
height: 90px;
width: 100vh;
padding: 0 30px;
background-color: green;
display: flex;
justify-content: space-between;
align-items: center;
transform: rotate(-90deg);
position: fixed;
top: 0;
right: 40px;
}
<div class="page"></div>
<div class="green-band">
<div class="text-inside">Text 1</div>
<div class="text-inside">Text 2</div>
<div class="text-inside">Text 3</div>
</div>
Can you help me figuring out how to correctly position the div?

.page {
width: 100%;
heigth: 100%;
background-color: #fefefe;
}
.green-band {
height: 90px;
width: 100vh;
padding: 0 30px;
background-color: green;
display: flex;
justify-content: space-between;
align-items: center;
transform: translateX(calc(100% - 40px)) rotate(-90deg);
transform-origin: bottom left;
position: fixed;
bottom: 0;
right: 0;
}
<div class="page"></div>
<div class="green-band">
<div class="text-inside">Text 1</div>
<div class="text-inside">Text 2</div>
<div class="text-inside">Text 3</div>
</div>

Align text in the center by ignoring the absolutely positioned element

I am developing a flex table from scratch and the table supports filtering and sorting. The icons for filters and sorting are displayed in the table header (right corner). Also my table supports that the user can position the header text left/center;
My problem:
Since the icons are inside the table header, icons as well occupies some space. So when i position the elements in the center, i see the alignment gets disturbed as shown below.
body {
width: 100%;
}
.table-header, .table-body {
display: flex;
width: fit-content;
border: 1px solid black;
padding: 10px;
}
.header, .data {
display: flex;
min-width: 150px;
width: 150px;
border-right: 1px solid black;
display: flex;
justify-content: center;
position: relative;
}
.header .text {
width: 100%;
white-space: nowrap;
text-align: center;
overflow: hidden;
text-overflow: ellipsis;
}
.icons {
float: right;
right: 0;
display: flex;
}
<div class="table">
<div class="table-header">
<div class="header">
<div class="text">Hlkjklkjlkjlkj lkjlkjlkjlkjlkjljlkjlkj</div>
<div class="icons">
<span> &#9760</span>
<span> &#9760</span>
</div>
</div>
<div class="header">9747
<div class="text">Header 2</div>
<div class="icons">
<span>b</span>
<span>b</span>
</div>
</div>
<div class="header">
<div class="text">Header 3</div>
<div class="icons">
<span>a</span>
<span>b</span>
</div>
</div>
<div class="header">
<div class="text">Header 4</div>
<div class="icons">
<span>a</span>
<span>b</span>
</div>
</div>
</div>
<div class="table-body">
<div class="data">123</div>
<div class="data">123</div>
<div class="data">123</div>
<div class="data">123</div>
</div>
<div class="table-body">
<div class="data">123</div>
<div class="data">123</div>
<div class="data">123</div>
<div class="data">123</div>
</div><div class="table-body">
<div class="data">123</div>
<div class="data">123</div>
<div class="data">123</div>
<div class="data">123</div>
</div>
</div>
Code: Here
What i tried
So since the icons as well take some space, to avoid this i positioned them absolutely relative to the header. So the alignment problem got solved . But for long headers where ellipsis has to be shown, the ellipsis hides behind the icons as shown below
Code: Here
So what is the solution to this ? I want to maintain the center position by reducing the space occupied by the icons. Is it possible through CSS? Please help. Thanks :)

If you try to do that with absolute positioning you need to know what exact width your icons can take.
Then possible solution is to add padding rule (left/right) into table headers, so CSS code should be like this:
body {
width: 100%;
}
.table-header, .table-body {
display: flex;
width: fit-content;
border: 1px solid black;
padding: 10px;
}
.header, .data {
box-sizing: border-box;
padding: 0 30px;
display: flex;
min-width: 150px;
width: 150px;
border-right: 1px solid black;
display: flex;
justify-content: center;
position: relative;
}
.header .text {
width: 100%;
white-space: nowrap;
text-align: center;
overflow: hidden;
text-overflow: ellipsis;
}
.icons {
position: absolute;
right: 0;
}

Center remaining bootstrap columns [duplicate]

How to center div horizontally, and vertically within the container using flexbox. In below example, I want each number below each other (in rows), which are centered horizontally.
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: flex;
align-items: center;
justify-content: center;
}
row {
width: 100%;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
}
<div class="flex-container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
http://codepen.io/anon/pen/zLxBo

I think you want something like the following.
html, body {
height: 100%;
}
body {
margin: 0;
}
.flex-container {
height: 100%;
padding: 0;
margin: 0;
display: flex;
align-items: center;
justify-content: center;
}
.row {
width: auto;
border: 1px solid blue;
}
.flex-item {
background-color: tomato;
padding: 5px;
width: 20px;
height: 20px;
margin: 10px;
line-height: 20px;
color: white;
font-weight: bold;
font-size: 2em;
text-align: center;
}
<div class="flex-container">
<div class="row">
<div class="flex-item">1</div>
<div class="flex-item">2</div>
<div class="flex-item">3</div>
<div class="flex-item">4</div>
</div>
</div>
See demo at: http://jsfiddle.net/audetwebdesign/tFscL/
Your .flex-item elements should be block level (div instead of span) if you want the height and top/bottom padding to work properly.
Also, on .row, set the width to auto instead of 100%.
Your .flex-container properties are fine.
If you want the .row to be centered vertically in the view port, assign 100% height to html and body, and also zero out the body margins.
Note that .flex-container needs a height to see the vertical alignment effect, otherwise, the container computes the minimum height needed to enclose the content, which is less than the view port height in this example.
Footnote:
The flex-flow, flex-direction, flex-wrap properties could have made this design easier to implement. I think that the .row container is not needed unless you want to add some styling around the elements (background image, borders and so on).
A useful resource is: http://demo.agektmr.com/flexbox/

How to Center Elements Vertically and Horizontally in Flexbox
Below are two general centering solutions.
One for vertically-aligned flex items (flex-direction: column) and the other for horizontally-aligned flex items (flex-direction: row).
In both cases the height of the centered divs can be variable, undefined, unknown, whatever. The height of the centered divs doesn't matter.
Here's the HTML for both:
<div id="container"><!-- flex container -->
<div class="box" id="bluebox"><!-- flex item -->
<p>DIV #1</p>
</div>
<div class="box" id="redbox"><!-- flex item -->
<p>DIV #2</p>
</div>
</div>
CSS (excluding decorative styles)
When flex items are stacked vertically:
#container {
display: flex; /* establish flex container */
flex-direction: column; /* make main axis vertical */
justify-content: center; /* center items vertically, in this case */
align-items: center; /* center items horizontally, in this case */
height: 300px;
}
.box {
width: 300px;
margin: 5px;
text-align: center; /* will center text in <p>, which is not a flex item */
}
DEMO
When flex items are stacked horizontally:
Adjust the flex-direction rule from the code above.
#container {
display: flex;
flex-direction: row; /* make main axis horizontal (default setting) */
justify-content: center; /* center items horizontally, in this case */
align-items: center; /* center items vertically, in this case */
height: 300px;
}
DEMO
Centering the content of the flex items
The scope of a flex formatting context is limited to a parent-child relationship. Descendants of a flex container beyond the children do not participate in flex layout and will ignore flex properties. Essentially, flex properties are not inheritable beyond the children.
Hence, you will always need to apply display: flex or display: inline-flex to a parent element in order to apply flex properties to the child.
In order to vertically and/or horizontally center text or other content contained in a flex item, make the item a (nested) flex container, and repeat the centering rules.
.box {
display: flex;
justify-content: center;
align-items: center; /* for single line flex container */
align-content: center; /* for multi-line flex container */
}
More details here: How to vertically align text inside a flexbox?
Alternatively, you can apply margin: auto to the content element of the flex item.
p { margin: auto; }
Learn about flex auto margins here: Methods for Aligning Flex Items (see box#56).
Centering multiple lines of flex items
When a flex container has multiple lines (due to wrapping) the align-content property will be necessary for cross-axis alignment.
From the spec:
8.4. Packing Flex Lines: the align-content
property
The align-content property aligns a flex container’s lines within the
flex container when there is extra space in the cross-axis, similar to
how justify-content aligns individual items within the main-axis.
Note, this property has no effect on a single-line flex container.
More details here: How does flex-wrap work with align-self, align-items and align-content?
Browser support
Flexbox is supported by all major browsers, except IE < 10. Some recent browser versions, such as Safari 8 and IE10, require vendor prefixes. For a quick way to add prefixes use Autoprefixer. More details in this answer.
Centering solution for older browsers
For an alternative centering solution using CSS table and positioning properties see this answer: https://stackoverflow.com/a/31977476/3597276

Add
.container {
display: flex;
justify-content: center;
align-items: center;
}
to the container element of whatever you want to center. Documentation:
justify-content and
align-items.

You can make use of
display: flex;
align-items: center;
justify-content: center;
on your parent component

Don't forgot to use important browsers specific attributes:
align-items: center; -->
-webkit-box-align: center;
-moz-box-align: center;
-ms-flex-align: center;
-webkit-align-items: center;
align-items: center;
justify-content: center; -->
-webkit-box-pack: center;
-moz-box-pack: center;
-ms-flex-pack: center;
-webkit-justify-content: center;
justify-content: center;
You could read this two links for better understanding flex:
http://css-tricks.com/almanac/properties/j/justify-content/ and
http://ptb2.me/flexbox/
Good Luck.

Use this:
html, body {
display: flex;
align-items: center;
justify-content: center;
height: 100%;
}
for some HTML markup like this:
<html>
<body>
<main>
<button> abc </button>
<p> something </p>
</main>
</body>
</html>
html, body {
display: flex;
align-items: center;
justify-content: center;
height: 100%;
}
<html>
<body>
<main>
<button> abc </button>
<p> something </p>
</main>
</body>
</html>

1 - Set CSS on parent div to display: flex;
2 - Set CSS on parent div to flex-direction: column; Note that this will make all content within that div line up top to bottom. This will work best if the parent div only contains the child and nothing else.
3 - Set CSS on parent div to justify-content: center;
Here is an example of what the CSS will look like:
.parentDivClass {
display: flex;
flex-direction: column;
justify-content: center;
}

diplay: flex; for it's container and margin:auto; for it's item works perfect.
NOTE: You have to setup the width and height to see the effect.
#container{
width: 100%; /*width needs to be setup*/
height: 150px; /*height needs to be setup*/
display: flex;
}
.item{
margin: auto; /*These will make the item in center*/
background-color: #CCC;
}
<div id="container">
<div class="item">CENTER</div>
</div>

margin: auto works "perfectly" with flexbox i.e. it allows to center item vertically and horizontally.
html, body {
height: 100%;
max-height: 100%;
}
.flex-container {
display: flex;
height: 100%;
background-color: green;
}
.container {
display: flex;
margin: auto;
}
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>JS</title>
</head>
<body>
<div class="flex-container">
<div class="container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
</div>
</body>
</html>

If you need to center a text in a link this will do the trick:
div {
display: flex;
width: 200px;
height: 80px;
background-color: yellow;
}
a {
display: flex;
align-items: center;
justify-content: center;
text-align: center; /* only important for multiple lines */
padding: 0 20px;
background-color: silver;
border: 2px solid blue;
}
<div>
text
text with two lines
</div>

RESULT:
CODE
HTML:
<div class="flex-container">
<div class="rows">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
</div>
CSS:
html, body {
height: 100%;
}
.flex-container {
display: flex;
justify-content: center;
align-items: center;
height: 100%;
}
.rows {
display: flex;
flex-direction: column;
}
where flex-container div is used to center vertically and horizontally your rows div, and rows div is used to group your "items" and ordering them in a column based one.

You can add flex-direction:column to flex-container
.flex-container {
flex-direction: column;
}
Add display:inline-block to flex-item
.flex-item {
display: inline-block;
}
because you added width and height has no effect on this element since it has a display of inline. Try adding display:inline-block or display:block. Learn more about width and height.
Also add to row class( you are given row{} not taken as style)
.row{
width:100%;
margin:0 auto;
text-align:center;
}
Working Demo in Row :
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: flex;
align-items: center;
justify-content:center;
flex-direction:column;
}
.row{
width:100%;
margin:0 auto;
text-align:center;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
display: inline-block;
}
<div class="flex-container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
Working Demo in Column :
.flex-container {
padding: 0;
margin: 0;
width: 100%;
list-style: none;
display: flex;
align-items: center;
}
.row {
width: 100%;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
display: inline-block;
}
<div class="flex-container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>

Hope this will help.
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: flex;
align-items: center;
justify-content: center;
}
row {
width: 100%;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
}

Using CSS+
<div class="EXTENDER">
<div class="PADDER-CENTER">
<div contentEditable="true">Edit this text...</div>
</div>
</div>
take a look HERE

Modal not displaying in center of page with flexbox [duplicate]

How to center div horizontally, and vertically within the container using flexbox. In below example, I want each number below each other (in rows), which are centered horizontally.
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: flex;
align-items: center;
justify-content: center;
}
row {
width: 100%;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
}
<div class="flex-container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
http://codepen.io/anon/pen/zLxBo

I think you want something like the following.
html, body {
height: 100%;
}
body {
margin: 0;
}
.flex-container {
height: 100%;
padding: 0;
margin: 0;
display: flex;
align-items: center;
justify-content: center;
}
.row {
width: auto;
border: 1px solid blue;
}
.flex-item {
background-color: tomato;
padding: 5px;
width: 20px;
height: 20px;
margin: 10px;
line-height: 20px;
color: white;
font-weight: bold;
font-size: 2em;
text-align: center;
}
<div class="flex-container">
<div class="row">
<div class="flex-item">1</div>
<div class="flex-item">2</div>
<div class="flex-item">3</div>
<div class="flex-item">4</div>
</div>
</div>
See demo at: http://jsfiddle.net/audetwebdesign/tFscL/
Your .flex-item elements should be block level (div instead of span) if you want the height and top/bottom padding to work properly.
Also, on .row, set the width to auto instead of 100%.
Your .flex-container properties are fine.
If you want the .row to be centered vertically in the view port, assign 100% height to html and body, and also zero out the body margins.
Note that .flex-container needs a height to see the vertical alignment effect, otherwise, the container computes the minimum height needed to enclose the content, which is less than the view port height in this example.
Footnote:
The flex-flow, flex-direction, flex-wrap properties could have made this design easier to implement. I think that the .row container is not needed unless you want to add some styling around the elements (background image, borders and so on).
A useful resource is: http://demo.agektmr.com/flexbox/

How to Center Elements Vertically and Horizontally in Flexbox
Below are two general centering solutions.
One for vertically-aligned flex items (flex-direction: column) and the other for horizontally-aligned flex items (flex-direction: row).
In both cases the height of the centered divs can be variable, undefined, unknown, whatever. The height of the centered divs doesn't matter.
Here's the HTML for both:
<div id="container"><!-- flex container -->
<div class="box" id="bluebox"><!-- flex item -->
<p>DIV #1</p>
</div>
<div class="box" id="redbox"><!-- flex item -->
<p>DIV #2</p>
</div>
</div>
CSS (excluding decorative styles)
When flex items are stacked vertically:
#container {
display: flex; /* establish flex container */
flex-direction: column; /* make main axis vertical */
justify-content: center; /* center items vertically, in this case */
align-items: center; /* center items horizontally, in this case */
height: 300px;
}
.box {
width: 300px;
margin: 5px;
text-align: center; /* will center text in <p>, which is not a flex item */
}
DEMO
When flex items are stacked horizontally:
Adjust the flex-direction rule from the code above.
#container {
display: flex;
flex-direction: row; /* make main axis horizontal (default setting) */
justify-content: center; /* center items horizontally, in this case */
align-items: center; /* center items vertically, in this case */
height: 300px;
}
DEMO
Centering the content of the flex items
The scope of a flex formatting context is limited to a parent-child relationship. Descendants of a flex container beyond the children do not participate in flex layout and will ignore flex properties. Essentially, flex properties are not inheritable beyond the children.
Hence, you will always need to apply display: flex or display: inline-flex to a parent element in order to apply flex properties to the child.
In order to vertically and/or horizontally center text or other content contained in a flex item, make the item a (nested) flex container, and repeat the centering rules.
.box {
display: flex;
justify-content: center;
align-items: center; /* for single line flex container */
align-content: center; /* for multi-line flex container */
}
More details here: How to vertically align text inside a flexbox?
Alternatively, you can apply margin: auto to the content element of the flex item.
p { margin: auto; }
Learn about flex auto margins here: Methods for Aligning Flex Items (see box#56).
Centering multiple lines of flex items
When a flex container has multiple lines (due to wrapping) the align-content property will be necessary for cross-axis alignment.
From the spec:
8.4. Packing Flex Lines: the align-content
property
The align-content property aligns a flex container’s lines within the
flex container when there is extra space in the cross-axis, similar to
how justify-content aligns individual items within the main-axis.
Note, this property has no effect on a single-line flex container.
More details here: How does flex-wrap work with align-self, align-items and align-content?
Browser support
Flexbox is supported by all major browsers, except IE < 10. Some recent browser versions, such as Safari 8 and IE10, require vendor prefixes. For a quick way to add prefixes use Autoprefixer. More details in this answer.
Centering solution for older browsers
For an alternative centering solution using CSS table and positioning properties see this answer: https://stackoverflow.com/a/31977476/3597276

Add
.container {
display: flex;
justify-content: center;
align-items: center;
}
to the container element of whatever you want to center. Documentation:
justify-content and
align-items.

You can make use of
display: flex;
align-items: center;
justify-content: center;
on your parent component

Don't forgot to use important browsers specific attributes:
align-items: center; -->
-webkit-box-align: center;
-moz-box-align: center;
-ms-flex-align: center;
-webkit-align-items: center;
align-items: center;
justify-content: center; -->
-webkit-box-pack: center;
-moz-box-pack: center;
-ms-flex-pack: center;
-webkit-justify-content: center;
justify-content: center;
You could read this two links for better understanding flex:
http://css-tricks.com/almanac/properties/j/justify-content/ and
http://ptb2.me/flexbox/
Good Luck.

Use this:
html, body {
display: flex;
align-items: center;
justify-content: center;
height: 100%;
}
for some HTML markup like this:
<html>
<body>
<main>
<button> abc </button>
<p> something </p>
</main>
</body>
</html>
html, body {
display: flex;
align-items: center;
justify-content: center;
height: 100%;
}
<html>
<body>
<main>
<button> abc </button>
<p> something </p>
</main>
</body>
</html>

1 - Set CSS on parent div to display: flex;
2 - Set CSS on parent div to flex-direction: column; Note that this will make all content within that div line up top to bottom. This will work best if the parent div only contains the child and nothing else.
3 - Set CSS on parent div to justify-content: center;
Here is an example of what the CSS will look like:
.parentDivClass {
display: flex;
flex-direction: column;
justify-content: center;
}

diplay: flex; for it's container and margin:auto; for it's item works perfect.
NOTE: You have to setup the width and height to see the effect.
#container{
width: 100%; /*width needs to be setup*/
height: 150px; /*height needs to be setup*/
display: flex;
}
.item{
margin: auto; /*These will make the item in center*/
background-color: #CCC;
}
<div id="container">
<div class="item">CENTER</div>
</div>

margin: auto works "perfectly" with flexbox i.e. it allows to center item vertically and horizontally.
html, body {
height: 100%;
max-height: 100%;
}
.flex-container {
display: flex;
height: 100%;
background-color: green;
}
.container {
display: flex;
margin: auto;
}
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>JS</title>
</head>
<body>
<div class="flex-container">
<div class="container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
</div>
</body>
</html>

If you need to center a text in a link this will do the trick:
div {
display: flex;
width: 200px;
height: 80px;
background-color: yellow;
}
a {
display: flex;
align-items: center;
justify-content: center;
text-align: center; /* only important for multiple lines */
padding: 0 20px;
background-color: silver;
border: 2px solid blue;
}
<div>
text
text with two lines
</div>

RESULT:
CODE
HTML:
<div class="flex-container">
<div class="rows">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
</div>
CSS:
html, body {
height: 100%;
}
.flex-container {
display: flex;
justify-content: center;
align-items: center;
height: 100%;
}
.rows {
display: flex;
flex-direction: column;
}
where flex-container div is used to center vertically and horizontally your rows div, and rows div is used to group your "items" and ordering them in a column based one.

You can add flex-direction:column to flex-container
.flex-container {
flex-direction: column;
}
Add display:inline-block to flex-item
.flex-item {
display: inline-block;
}
because you added width and height has no effect on this element since it has a display of inline. Try adding display:inline-block or display:block. Learn more about width and height.
Also add to row class( you are given row{} not taken as style)
.row{
width:100%;
margin:0 auto;
text-align:center;
}
Working Demo in Row :
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: flex;
align-items: center;
justify-content:center;
flex-direction:column;
}
.row{
width:100%;
margin:0 auto;
text-align:center;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
display: inline-block;
}
<div class="flex-container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>
Working Demo in Column :
.flex-container {
padding: 0;
margin: 0;
width: 100%;
list-style: none;
display: flex;
align-items: center;
}
.row {
width: 100%;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
display: inline-block;
}
<div class="flex-container">
<div class="row">
<span class="flex-item">1</span>
</div>
<div class="row">
<span class="flex-item">2</span>
</div>
<div class="row">
<span class="flex-item">3</span>
</div>
<div class="row">
<span class="flex-item">4</span>
</div>
</div>

Hope this will help.
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: flex;
align-items: center;
justify-content: center;
}
row {
width: 100%;
}
.flex-item {
background: tomato;
padding: 5px;
width: 200px;
height: 150px;
margin: 10px;
line-height: 150px;
color: white;
font-weight: bold;
font-size: 3em;
text-align: center;
}

Using CSS+
<div class="EXTENDER">
<div class="PADDER-CENTER">
<div contentEditable="true">Edit this text...</div>
</div>
</div>
take a look HERE