Following my question, I have some CSS, but because the textarea lies inside the div that plays the role of a page, it won't work have any effect. Can I somehow do that? The only think that matters to be is to get the border nice and to get the textarea relatively small (now it will take all the width of the screen), like in my fiddle.
textarea {
display: block;
box-sizing: padding-box;
overflow: hidden;
padding: 10px;
width: 250px;
font-size: 14px;
margin: 50px auto;
border-radius: 8px;
border: 6px solid #556677;
width: 30%;
}