When I do an HTML export of my org buffer, it produces a default css
section in the head:

<style type="text/css">
 <!--/*--><![CDATA[/*><!--*/
  .title  { text-align: center;
             margin-bottom: .2em; }
  .subtitle { text-align: center;
              font-size: medium;
              font-weight: bold;
              margin-top:0; }
. . .

The docs (http://orgmode.org/manual/CSS-support.html#CSS-support) seem to
be saying this can be overridden by a style sheet I may want to add. Is
this an accurate assumption. In other words, in my own stylesheet.css I can
make the border and drop shadow around a code block result go away by
overriding it. Correct?

What is producing this default css styling and how can I change it directly?

LB