html, body { margin: 0; padding: 0; }
<!--[if IE]>
html {
background: url(http://www.aws.gr/images/sbg.gif) repeat-x fixed left top; 
overflow: hidden;
}
html body {
background: url(http://www.aws.gr/images/background.gif) repeat-x fixed center top; 
overflow: auto;
}
<!--[endif]-->	

<!--[if NOT IE]>
html { background: url(http://www.aws.gr/images/sbg.gif) repeat-x fixed left top;}
html body { background: url(http://www.aws.gr/images/background.gif) repeat-x fixed center top;}
<!--[endif]-->

body { text-align: center; }