How to align the inside box to center of the table - html

Question

I have the table, inside the table I have another box , I am struggling to align the box in center of the table.
My CSS code is
Inside box code
.inside_box{
border: medium solid;
display: table-cell;
float: none;
font-family: Helvetica-bold;
font-size: 20.19px;
height: 100px;
margin: auto;
text-align: center;
vertical-align: middle;
width: 300px;
}
Outside table CSS:
.outer_table {
border: 1px solid black;
border-radius: 5px;
color: #1A6DAC;
font-size: 24px;
left: 40px;
padding: 20px;
position: absolute;
top: 260px;
width: 740px;
}
How to align the inside box in center?

Answer 1

I assume that your HTML is something like this
<div class="outer_table">
<div class="inside_box">hello world</div>
</div>
So, you are using display: table-cell; for .inside_box and margin: auto; won't work, as it's a table cell now, so what you can do is, wrap a div around hello world text, like this
Demo
<div class="outer_table">
<div class="inside_box"><div>hello world</div></div>
</div>
And use CSS like
.inside_box {
border: medium solid;
display: table;
font-family: Helvetica-bold;
font-size: 20.19px;
height: 100px;
margin: auto;
width: 300px;
}
.outer_table {
border: 1px solid black;
border-radius: 5px;
color: #1A6DAC;
font-size: 24px;
left: 40px;
padding: 20px;
position: absolute;
top: 260px;
width: 740px;
}
.inside_box > div {
display: table-cell;
text-align: center;
vertical-align: middle;
}
Make sure you port the text-align: center; and vertical-align: middle; properties from .inside_box to .inside_box > div selector block.
Note: You won't need float: none;, not sure why you are using that.
As I got a comment, that what if you do not want to add an extra div element, so think like that you are using td without a table tag. So there is no way for that div with display: table-cell; to respect margin: auto;.
From Mozilla Developer Network :

Answer 2

Try to change and make your css like this:
.outer_table td {
text-align: center; // Align center
}
.inside_box {
float: none; // if you set float left or right your box will move right there
margin: 0px auto; // this setting for balancing margin left and right
}
<table class="outer_table">
<tr><td><div class="inside_box">Hellow wolrd!</div></td></tr>
</table>