why firefox adds css styles unexpectedly?

Question

The css is exactly like this:

body {
    background:#FFFFFF none repeat scroll 0;
    margin:2px 5px;
    font-family:Arial,sans-serif;
    font-size:10pt;
}

But from firebug I see the style is:

body {
-moz-background-clip:border;
-moz-background-inline-policy:continuous;
-moz-background-origin:padding;
background:#FFFFFF none repeat scroll 0 50%;
font-family:Arial,sans-serif;
font-size:10pt;
margin:2px 5px;
}

Why does firefox add those un-needed styles? How can I get rid of them?

Answer 1

It is not adding anything for me. Are you sure these are not default styles saved in your default user stylesheet?

Answer 2

It is added by the rendering engine for its own use, so you cannot get rid of them. See this question for details.