URGENT: Sending divs behind each other

Code:

---

#header{
        background:url(images/header-background.png) no-repeat;
        width:100%;
        height:100%;
}

#curve{
        background:url(images/curve.png);
        width:906px;
        height:358px;
        position:relative;
        top:30px;
}

#curve-down{
        background:url(images/curvedown.png);
        width:906px;
        height:427px;
        position:relative;
        top:85px;
}

---

And

Code:

---

        <div id="header">
               
                <div id="curve">               
                        <div id="curve-down">
                       
                        </div>
                </div>
       
        </div>

---

I want to send #curve on top of #curve-down. i tried z-index but it didn't work eighter. somebody help me please. i need an urgent help please.

Anyone please?

Can you please show us a visual example also ? Or just post the background images of these divs.

:wave: