how do i make this be positioned to the left

Code:
#navContainer
{
    background-image:url(images/nav.gif);
    position: relative;    
}
And this to the center??

Code:
#contentContainer
{
    background-image: url(images/content.gif);
    width: 567px;
    height: 379px;
    padding: 0px;
    padding-top: 25px;
    padding-left:10px;
    
    
}