Removing border throws out layout

[swollenpickles]

I'm trying to build a header template using CSS. I have the layout how I want it, in terms of the positioning of the sections, now I'm just trying to style it. When I try to get rid of the borders it throws the alignment out.
I'm sure what I'm screwing up is obvious, I just can't see it.
Here is an extract from the CSS i have so far:

#container	{
	width: 900px;
	margin: 0 auto;
}

#headerbox	{
	padding: 5px;
	background: #f9ff93;
	margin-bottom: 5px;
	border: 1px solid #000000;
}

#login	{
	float: right;
	width: 330px;
	height: 150px;
	background: #ffcb99;
	border: 1px solid #000000;
}

#title	{
	width: 552px;
	height: 100px;
	background: #98cb00;
	margin-bottom: 5px;
	border: 1px solid #000000;
}

#topmenu	{
	width: 552px;
	height: 45px;
	background: #bae0e3;
	border: 1px solid #000000;
}

[Dan_A]

A link to the page would give better answers.
Most of the time the answer is here :
http://www.search-this.com/2007/03/1...rgin-for-error
or here :
http://complexspiral.com/publication...psing-margins/