vertical-align with Bootstrap 3

Issue

I'm using Twitter Bootstrap 3, and I have problems when I want to align vertically two div, for example — JSFiddle link:

<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">

<!-- Optional theme -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap-theme.min.css">

<!-- Latest compiled and minified JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<div class="row">
  <div class="col-xs-5">
    <div style="height:5em;border:1px solid #000">Big</div>
  </div>
  <div class="col-xs-5">
    <div style="height:3em;border:1px solid #F00">Small</div>
  </div>
</div>

The grid system in Bootstrap uses float: left, not display:inline-block, so the property vertical-align doesn't work. I tried using margin-top to fix it, but I think this is not a good solution for the responsive design.

Solution

This answer presents a hack, but I would highly recommend you to use flexbox (as stated in @Haschem answer), since it's now supported everywhere.

Demos link:
- Bootstrap 3
- Bootstrap 4 alpha 6

You still can use a custom class when you need it:

.vcenter {
    display: inline-block;
    vertical-align: middle;
    float: none;
}

<div class="row">
    <div class="col-xs-5 col-md-3 col-lg-1 vcenter">
        <div style="height:10em;border:1px solid #000">Big</div>
    </div><!--
    --><div class="col-xs-5 col-md-7 col-lg-9 vcenter">
        <div style="height:3em;border:1px solid #F00">Small</div>
    </div>
</div>

Bootply

Using inline-block adds extra space between blocks if you let a real space in your code (like ...</div> </div>...). This extra space breaks our grid if column sizes add up to 12:

<div class="row">
    <div class="col-xs-6 col-md-4 col-lg-2 vcenter">
        <div style="height:10em;border:1px solid #000">Big</div>
    </div>
    <div class="col-xs-6 col-md-8 col-lg-10 vcenter">
        <div style="height:3em;border:1px solid #F00">Small</div>
    </div>
</div>

Here, we've got extra spaces between <div class="[...] col-lg-2"> and <div class="[...] col-lg-10"> (a carriage return and 2 tabs/8 spaces). And so...

Let's kick this extra space!!

<div class="row">
    <div class="col-xs-6 col-md-4 col-lg-2 vcenter">
        <div style="height:10em;border:1px solid #000">Big</div>
    </div><!--
    --><div class="col-xs-6 col-md-8 col-lg-10 vcenter">
        <div style="height:3em;border:1px solid #F00">Small</div>
    </div>
</div>

Notice the seemingly useless comments <!-- ... -->? They are important -- without them, the whitespace between the <div> elements will take up space in the layout, breaking the grid system.

Note: the Bootply has been updated

Answered By - zessx