hi

i have problem with this piece of code
i've search but i couldn't find any answer for this problem

please see this code

Code:
<div style="width:700px; height:100px; background:#ccc;">
	<h1 style="font:10pt tahoma; margin:30px; background:#eee;">hello</h1>
</div>
IE (7, 6):



firefox, opera:



im using xhtml 1.0 doctype
it seems that opera and firefox ignore margin that applied to h1 tag but IE take that margin into account.

when i change the code to this form:

Code:
<div style="width:700px; height:100px; background:#ccc; border:1px solid #fff;">
	<h1 style="font:10pt tahoma; margin:30px; background:#eee;">hello</h1>
</div>
just with adding 1px border to div tag, all browsers show the page correctly and opera and firefox won't ignore margin his time.

what is the problem

thanks in advance