Just to followup on my CSS, the following should center the content pretty well on most setups - I can’t figure out why I have to manually set the height though, but if I don’t the border doesn’t draw around all the text.
This creates something like a “pop-up” in the middle of your screen for the content, which works pretty well for me.
transform: translate(-50%,-50%); // This centers the box
width: 80vw; // set the width to about 80% of the screen
height: 20vw; // set the height to about 20% of the screen