I currently have this div:
<div style="background: lightsalmon;margin-bottom: 12px; width: 600px; padding: 5px 8px;border: 1px solid #071B36;border-radius: 3px;">
    TEST
</div>
I have tried using <div style="text-align:center;"> </div> like this:
<div style='text-align: center;'>
    <div style="background: lightsalmon;margin-bottom: 12px; width: 600px; padding: 5px 8px;border: 1px solid #071B36;border-radius: 3px;">
        TEST
    </div>
</div>
^ Doesn't work
I've also tried using <div style="text-align:center; display:block;"> </div> like this:
<div style='text-align: center;  display:block;'>
    <div style="background: lightsalmon;margin-bottom: 12px; width: 600px; padding: 5px 8px;border: 1px solid #071B36;border-radius: 3px;">
        TEST
    </div>
</div>
^ Doesn't work
I've also tried using <center> </center> (even though it is not recommended... 
<center>
    <div style="background: lightsalmon;margin-bottom: 12px; width: 600px; padding: 5px 8px;border: 1px solid #071B36;border-radius: 3px;">
        TEST
    </div>
</center>
^ It works!!!
The only problem is that <center> is terrible to use as it is outdated! So how can I do this without using <center>
 
     
    