Box position not centering - html

Question

Im trying to center a box 200 by 200. I have tried using left:50% top:50% etc., but this is somehow not really working.
I created a fiddle to recreate my problem: https://jsfiddle.net/8k9o9Lvv/2/
I also tried to center the text from the top as well, with text-align:center and this is also not working.
Any ideas why this is not working?
HTML
<div id ="container">
<div class="slider-text">
<h2>Test</h2>
</div>
</div>
CSS
#container{
width:100%;
}
.slider-text {
text-align:center;
position:relative;
height:200px;
width: 200px;
border-left:1px solid red;
border-right:1px solid red;
border-top:1px solid red;
border-bottom:1px solid red;
top:50%;
left:50%;
right:50%;
}

Answer 1

Just margin:0px auto; is enough
#container {
width: 100%;
}
.slider-text {
text-align: center;
margin:0px auto;
height: 200px;
width: 200px;
border-left: 1px solid red;
border-right: 1px solid red;
border-top: 1px solid red;
border-bottom: 1px solid red;
}
<div id="container">
<div class="slider-text">
<h2>Test
</h2>
</div>
</div>

Answer 2

Give the below code a try, centering the #container div horizontally, and the .slider-text div horizontally and vertically within #container.
#container{
width:100%;
}
.slider-text {
text-align:center;
position:relative;
height:200px;
width: 200px;
border:1px solid red; /* Creates a border around entire element */
margin: auto; /* Centers horizontally */
}
/* This is to center the text vertically within its parent, */
/* remove it if you don't want to do that */
.slider-text h2 {
text-align:center;
position: absolute; /* position: relative; works too */
width: 100%;
top: 30%;
left: 0%;
}
<div id ="container">
<div class="slider-text">
<h2>Test</h2>
</div>
</div>
Let me know if it helps.

Answer 3

* {
margin: 0;
padding: 0;
}
#container{
position:relative;
width:100%;
height: 100vh;
}
.slider-text {
position: absolute;
text-align:center;
height:200px;
width: 200px;
border-left:1px solid red;
border-right:1px solid red;
border-top:1px solid red;
border-bottom:1px solid red;
top:50%;
left:50%;
transform: translateX(-50%) translateY(-50%);
right:50%;
display: flex;
align-items: center;
justify-content: center;
}
<div id ="container">
<div class="slider-text">
<h2>Test</h2>
</div>
</div>
You need to set the height of the container. In this case I used 100vh which is equal to 1 viewport height. transform: translateX(-50%) translateY(-50%); with top: 50%; left: 50% will make your .slider-text on center.
To center your text. You can use flexbox. Using display: flex will enable you to use align-items and justify-content. With value of center, it will allow your text to flow on center of its parent.

Answer 4

Your HTML
<div id ="container">
<div class="slider-text">
<h2>Test</h2>
</div>
</div>
Modified CSS
#container{
width:100%;
}
.slider-text {
position:relative;
height:200px;
width: 200px;
border:1px solid red;
margin: 0 auto;
}
.slider-text h2 {
width: 100%;
text-align: center;
}

Answer 5

#container{
width:100%;
position: relative;
}
.slider-text {
text-align:center;
height:200px;
width: 200px;
border-left:1px solid red;
border-right:1px solid red;
border-top:1px solid red;
border-bottom:1px solid red;
position: relative;
}
/*since slider-text has a fixed height and width, a simple math would do*/
.slider-text h2 {
margin-top: 90px;
}
<div id ="container">
<div class="slider-text"><h2>Test
</h2></div>
</div>
Just a simple calculation would do

Answer 6

You should set height:100% to all elements down to your container. That means:
html, body, #container
{
height:100%;
}
Then to center horizontaly and verically a known-size div inside your #container, you just need to set for that div:
left:50%;
top:50%;
and
margin-left:(MINUS whatever is the half of your div width)
margin-top:(MINUS whatever is the half of your div height)
UPDATED FIDDLE (sorry forgot to "update" it)
edit: i assumed you want to center it to the whole screen.

Answer 7

Assuming you want to center it both X and Y, you're right so far, however there are a few changes. Use this for your .slider-text class:
.slider-text {
text-align:center;
position:absolute; /* Relative was wrong */
height:200px;
width: 200px;
border-left:1px solid red;
border-right:1px solid red;
border-top:1px solid red;
border-bottom:1px solid red;
top:50%;
left:50%;
transform: translate(-50%,-50%);
}
Relative positioning was incorrect in this instance. absolute is correct. Relative would make it move X amount of pixels from its natural position, whereas absolute will position it in a specific place, relative to the closest parent with position: relative on it.
The transform basically does the same as negative margins, but you don't need to change the margin if the size of the box changes :)
Let me know if you have any questions.

Answer 8

Here is the css code:
.slider-text {
text-align:center;
position:absolute;
height:200px;
width: 200px;
border-left:1px solid red;
border-right:1px solid red;
border-top:1px solid red;
border-bottom:1px solid red;
top:50%;
left:50%;
margin-left:-100px;
margin-top:-100px;
}
margin-left:-(div width)/2;
margin-top:-(div height)/2;