sizing the comment popup

I searched the site to no avail. I have the $height, $width tags in the header, but it is not big enough and the typing box is to wide.

This is the code in my style.css
.commentHeader {
position: relative; /* Position is declared “relative” to gain control of stacking order (z-index). */
width: auto;
margin: 10px 10px 10px 10px;
border: 1px solid #000000;
background: #cccccc;
color: #000000;
padding: 10px;
z-index: 3; /* This allows the content to overlap the right menu in narrow windows in good browsers. */
font-size: 16px;
font-weight: 600;
}

Any idea, I am real new to this