iframe height problem

Hi,

I have this css:

#popup-background
{
    position: fixed;
    top: 0%;
    left: 0%;
    width: 100%;
    height: 100%;
    background-color: #000;
    z-index:1001;
    -moz-opacity: 0.4;
    opacity: 0.4;
    display: none;
}

#popup
{
    width: 600px;
    height: 400px;
    z-index: 1002;
    display: none;
    position: absolute;
    top:0;
    bottom: 0;
    left: 0;
    right: 0;
    margin: auto;
}

#frame
{
    width: 580px;
    height: 390px;
}

And this iframe:

<div id="popup-background" onclick="$('#popup-background').hide();$('#popup').hide();"></div><div id="popup"><iframe id="frame" src="../Boss_Travel_Orders/travel_orders_detail.aspx" frameborder="0"></iframe></div>

The popup-background is the gray background for the whole page, the popup is the div, which is showing and which has the iframe in it.

As you see, the popup div is a bit larger as the iframe. The iframe has the size 550x380.

Despite that, the vertical scrollbar is too big, because the iframe height size is too big, and I assume, it isn't 380 but higher.

What can be the problem?