Div will not go 100% wide

[streetbmx]

Im trying to make a div go accross the top of a page, all the way accross. In IE it will not go all the way accross, unless i change the width to 101%. But in Mozilla it works at 100% but at 101% it makes the page wider than the broswer window. Is there anyway to make this div truley 100% wide?

here is my css.

div.header {
background-color: #CCCCCC;
height: 90px;
width: 100%; /* the width in question */
border-bottom-width: 1px;
border-bottom-style: solid;
border-bottom-color: #000000;
margin: 0px;
position: absolute;
top: 0px;
left: 0px;
}
body {
margin: 0px;
padding: 0px;
}

 

[streetbmx]

Arg, ok 0 margin and padding works but it will not work if i have a margin or padding. Is there a way to fix that?