body {
  background-color: #D3D3D3;/*light/medium gray*/
/*  background-image: url("images/pat.jpg");*/
/*  background-repeat: repeat;*/
/* Not sure margin has desired effect here */
  margin-left: 10%;
  margin-right: 10%
 }

#main {
    background-color: #F0F0F0; /*very light gray*/
    /*background-image: url("images/pat.jpg");
    background-repeat: repeat;*/
    float: none;
    width: 780px;
/*    margin: 50px; doesn't seem to have any effect*/
/*    border: 50px; */
    padding: 20px;
}

h1 { 
/*    margin-left: -8%;*/
}

h2,h3,h4,h5,h6 { 
/*    margin-left: -4%;*/
}

img {
  margin: 10px;
  border: 0;
 }

pre { /* Don't make pre-formatted fonts larger */
    font-size: small;
}

#footer {
    width: 780px; 
    padding: 20px;
}