CSS

how to align elements horizontally in css

.row {
  width: 100%;
  display: flex;
  flex-direction: row;
  justify-content: center;
}
.block {
  width: 100px;
}

How to horizontally center an element

You can apply this CSS to the inner <div>:

#inner {
  width: 50%;
  margin: 0 auto;
}
Of course, you don't have to set the width to 50%. Any width less than the containing <div> will work. The margin: 0 auto is what does the actual centering.

If you are targeting Internet Explorer 8 (and later), it might be better to have this instead:

#inner {
  display: table;
  margin: 0 auto;
}
It will make the inner element center horizontally and it works without setting a specific width.

Working example here:

#inner {
  display: table;
  margin: 0 auto;
  border: 1px solid black;
}

#outer {
  border: 1px solid red;
  width:100%
}
<div id="outer">
  <div id="inner">Foo foo</div>
</div>

center div element horizontally

<div class="center">this content will be in the horizontally centered of your page</div>
<style>
/** this is the css to center a DIV or any element **/
.center {
  display: table;
  margin: 0 auto;
}
</style>

center element horizontally in div

#inner {
  display: table;
  margin: 0 auto;
  border: 1px solid black;
}

#outer {
  border: 1px solid red;
  width:100%
}

<-- Html -->

<div id="outer">
  <div id="inner">Foo foo</div>
</div>

html - How to horizontally center an element

You can apply this CSS to the inner <div>:

#inner {   width: 50%;   margin: 0 auto; } 
Of course, you don't have to set the width to 50%. Any width less than the containing <div> will work. The margin: 0 auto is what does the actual centering.

If you are targeting Internet Explorer 8 (and later), it might be better to have this instead:

#inner {   display: table;   margin: 0 auto; } 
It will make the inner element center horizontally and it works without setting a specific width.

Working example here:

#inner {   display: table;   margin: 0 auto;   border: 1px solid black; }  #outer {   border: 1px solid red;   width:100% }
<div id="outer">   <div id="inner">Foo foo</div> </div>
EDIT
With flexbox it is very easy to style the div horizontally and vertically centered.

#inner {     border: 1px solid black; }  #outer {   border: 1px solid red;   width:100%;   display: flex;   justify-content: center; }
<div id="outer">   <div id="inner">Foo foo</div> </div>
To align the div vertically centered, use the property align-items: center.

how to align elements horizontally in css

<div class="row">
  <div class="block">Lorem</div>
  <div class="block">Ipsum</div>
  <div class="block">Dolor</div>
</div>