Use

#body{
    /*style definitions intended only for the page*/
}

The editor has a body tag too, the body of the page has an id called body, so this way you set the styles only for the page itself

I'm having the same problem but have not yet been able to resolve it.  I'm using "body" and "#body" but my text/html is still using the background image for the "#body"  Here is what my CSS looks like:

body
{
 padding-right: 0px;
 padding-left: 0px;
 padding-bottom: 0px;
 margin: 0px;
 padding-top: 0px;
 background-color: #ffffff;
 text-align: center;
 background-image: none;
}

#body
{
 padding-right: 0px;
 padding-left: 0px;
 padding-bottom: 0px;
 margin: 0px;
 padding-top: 0px;
 background-color: #ffffff;
 text-align: center;
 background-image:url("img/pagebackground.jpg");
}