CSS Flex Not Working - html

Question

I want to justify a few images in a div.
I added justify-content: center;, but the images align left. Why?
.item {
justify-content: center;
}
<div class="item">
<div>
<img src="http://placehold.it/75x75" />
</div>
<div>
<img src="http://placehold.it/75x75" />
</div>
<div>
<img src="http://placehold.it/75x75" />
</div>
</div>​

Answer 1

The justify-content property only aligns the content/s of a given container if the container is a flexible one.
Add this to your CSS:
display: flex;
The full CSS code in the head section should be:
<style type="text/css">
.flex-item {
display: flex;
justify-content: center;
}
</style>
Source: http://www.w3schools.com/cssref/css3_pr_justify-content.asp
Example: http://www.w3schools.com/cssref/playit.asp?filename=playcss_justify-content&preval=center
Fidde example: https://jsfiddle.net/L4tmgs18/1/

Answer 2

If I understand correctly and you're trying to center the contents of the .flex-item div (i.e. the icons), replace justify-content: center; with text-align: center;.
Your problem isn't with how you have applied the css, that is correct, but depending on what you are trying to achieve, your problem is with the actual css used.

Answer 3

As I can see, you have all the necessary code provided to you by "Hubert Siwkin", but it sits a tad off the left side of your page. Simple fix. You need to edit your "body" CSS style and add a "margin" value.
body {
margin: 0px;
}
This will fix the problem you are facing.
If you would like to know more about the "body" CSS style, use the following link.
http://www.w3schools.com/tags/tag_body.asp
UPDATE: I have provided an update to the jsFiddle provided by "Hubert Siwkin". Most of the code that you have is not necessary, so I have slim-lined it for you.
https://jsfiddle.net/hddbkcvv/