html comment box cutting text without going onto new line

lukey

when i insert a comment more than the set width (600px) the text will just cut off (see image link above) instead of going onto a new line. I am using html comment box.
the style for the comment box is:

 #HCB_comment_box div.comment {
  border-top:1px solid #fff;
  width: 600px;

  }