How Can I Put Menu Over Iframe ???

[raul.lnx]

(sorry i speak english a little bit )

As you can see in mi website http://www.snowboard-zamora.net/ , i have a horizontal menu, and below it, there is a google adsense iframe. The problem is when the menu has 4 or more submenus .... This submenos are behind the iframe, and people can't see them.
You can see the effect in the last option in the menú "TRUCOTECA" ........

I'm trying with zindex in the layout of my template, but don't work, or i'm doing something wrong ......

If someone can help me ......... thanks ..........

[raul.lnx]

Yeah. Now It's Working !

With :

    div#menu_horiz {
        width: 100%;
        text-align: left;
position: absolute;
z-index: 1;
    }