Center webpage with absolute positions?

[CrapH]

the simplest code is

.main-background
{
  margin: 0 auto;
  padding: 0;
  background-color: #DBE5EB;
  background-image: url('images/page_t.jpg');
  background-repeat: no-repeat;
  background-attachment: fixed;
  background-position: top center;
  font-family: Arial, Helvetica, Sans-Serif;
  font-style: normal;
  font-weight: normal;
  font-size: 12px;
  color: #40535E;
} 

this is what i use for image backgrounds