Here is an interesting bug in browser's support of width property. Note try adding 'width: 100%;' in the div and check in both IE and Mozilla. You'll notice that with the width specified in the div, IE bahaves properly but Mozilla/NS makes the table too wide (like in the original case with IE6+). I'd love to hear of your solutions.

---START---
<?xml version="1.0" encoding="us-ascii"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US" lang="en-US">
<head>
<title>test table inside a div with margin and padding</title>
</head>
<body>
<div style="border: 2px solid yellow; margin: 50px;">
<table style="border: 1px solid red; width: 100%;">
<tr><td>
<p>In IE 6.x this table with a red border with be wider
than the maximized browser window. It's right edge will
be about 50 pixels beyond the brower's vertical scroll bar.
If you increase of decrease the <div>'s margin the "over-expanded"
area will be decreased by the same amount.</p>

<p>Why? Is this a bug in IE? It doesn't happen in Mozilla 1.2+
or NS6+.</p>
</td></tr>
</table>
</div>
</body>
</html>
---END---