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And finally: you can even import/load bootstrap inline with using CodeMirror Editor in Joomla if it's not loaded in default in your page. You can load bootstrap in a module if it's not loaded and use styling as you want. I mostly use uikit library for styling.

And finally: you can even import/load bootstrap inline with using CodeMirror Editor in Joomla if it's not loaded in default in your page. You can load bootstrap in an 'empty' module if it's not loaded and you can use bootstrap styling too as you want. I mostly use uikit library in layouts and styling.

And finally: you can even import/load bootstrap inline with using CodeMirror Editor in Joomla if it's not loaded in default in your page. You can load bootstrap in a module if it's not loaded and use styling as you want. I mostly use uikit library for styling.

So if you just copy and paste this code in your article you get 3 columns divs in the article, using bootstrap (this is just an example, not how you should load bootstrap for long term):

<div class="col">
  <div class="coll_1">
    <p>
      This is row1 1
    </p>
  </div>
  <div class="coll_2">
    <p>
      This is row2 2
    </p>
  </div>
  <div class="coll_3">
    <p>
      This is row 3
    </p>
  </div>
</div>

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<div class="container-fluid">
   <div class="row">
    <div class="col-sm">
      One of three columns
    </div>
    <div class="col-sm">
      Second of three columns
    </div>
    <div class="col-sm">
      Third of three columns
    </div>
  </div>
</div>


<style>
.coll_1 {
  width: 100px;
  height: 50px;
  background-color: red;
}

.coll_2 {
  width: 200px;
  height:50px;
  background-color: blue;
}
  
.coll_3 {
  width: 100px;
  height: 50px;
  }
</style> 

and the result with using Bootstrap where you can see the 3 columns division:

So you can do endless things using CodeMirror editor in Joomla.

You can place all of your custom css definitions in yourjoomla/templates/yourtemplate/css folder if you create a custom.css or user.css file in this folder. Since this does not always work with every templates, then you can use a free plugin to load your custom css codes/style:

https://extensions.joomla.org/extension/add-custom-css/

This way you can reuse your 'special' div class styles in other articles too and you do not have to define div styles article by article...

And I really forgot to mention that you need to use for example CodeMirror editor in your Joomla and you can edit the articles in full html mode in that case, which you can set at Global configuration->Default Editor->Editor-CodeMirror . And that way together with the above styling solution or with inline styling you can create any kind of html pages/articles. (I am sorry for leaving out this important part from my answer earlier).

Very important in using this css loading plugin: you have to put this plugin at the end of the plugin order in the Plug-in Manager.

Results of my test of the above:

My article html:

<div class="col">
  <div class="coll_1">
    <p>
      This is col 1
    </p>
  </div>
  <div class="coll_2">
    <p>
      This is col 2
    </p>
  </div>
</div>

my short css in custom.css file:

.coll_1 {
  width: 100px;
  height: 50px;
  background-color: red;
}

.coll_2 {
  width: 200px;
  height:50px;
  background-color: blue;
}

And my visual result in the article in Joomla frontend:

So it works without a problem.

But make the whole subject much more simple: if you use CodeMirror as your default editor in Joomla, then you actually do not need the Add Custom CSS Plugin for styling your articles. Using CodeMirror editor, you can just place your inline css style within <style> tags in the article, save the article, and you will have the same result (a styled article), so just paste the whole thing in one in the article and you will have that.

So then your article should just look like this:

<div class="col">
  <div class="coll_1">
    <p>
      This is col 1
    </p>
  </div>
  <div class="coll_2">
    <p>
      This is col 2
    </p>
  </div>
</div>

<style>
.coll_1 {
  width: 100px;
  height: 50px;
  background-color: red;
}

.coll_2 {
  width: 200px;
  height:50px;
  background-color: blue;
}
</style>

You can place all of your custom css definitions in yourjoomla/templates/yourtemplate/css folder if you create a custom.css or user.css file in this folder. Since this does not always work with every templates, then you can use a free plugin to load your custom css codes/style:

https://extensions.joomla.org/extension/add-custom-css/

This way you can reuse your 'special' div class styles in other articles too and you do not have to define div styles article by article...

And I really forgot to mention that you need to use for example CodeMirror editor in your Joomla and you can edit the articles in full html mode in that case, which you can set at Global configuration->Default Editor->Editor-CodeMirror . And that way together with the above styling solution or with inline styling you can create any kind of html pages/articles. (I am sorry for leaving out this important part from my answer earlier).

Very important in using this css loading plugin: you have to put this plugin at the end of the plugin order in the Plug-in Manager.

Results of my test of the above:

My article html:

<div class="col">
  <div class="coll_1">
    <p>
      This is col 1
    </p>
  </div>
  <div class="coll_2">
    <p>
      This is col 2
    </p>
  </div>
</div>

my short css in custom.css file:

.coll_1 {
  width: 100px;
  height: 50px;
  background-color: red;
}

.coll_2 {
  width: 200px;
  height:50px;
  background-color: blue;
}

And my visual result in the article in Joomla frontend:

So it works without a problem.

But making the whole subject much more simple: if you use CodeMirror as your default editor in Joomla, then you actually do not need the Add Custom CSS Plugin for styling your articles. Using CodeMirror editor, you can just place your inline css style within <style> tags in the article, save the article, and you will have the same result (a styled article), so just paste the whole thing in one in the article and you will have that.

So then your article should just look like this:

<div class="col">
  <div class="coll_1">
    <p>
      This is col 1
    </p>
  </div>
  <div class="coll_2">
    <p>
      This is col 2
    </p>
  </div>
</div>

<style>
.coll_1 {
  width: 100px;
  height: 50px;
  background-color: red;
}

.coll_2 {
  width: 200px;
  height:50px;
  background-color: blue;
}
</style>