z-index with fixed position? :S

$("body").append($("#Stage_Iframe").css("position", "fixed"));

var container = sym.$('#Stage_Iframe');

var Frame = ' <div class="Frame" id="Frame"><iframe width="100%" height="600" src="http://apliix.net78.net/video.html" frameborder="0" allowfullscreen></iframe></div> '

container.html(Frame);

So As you can see Stage_Iframe is fixed and doesn't move even if someone scrolls the page that's good, working but how do I get the Stage_Iframe to be behind all other conent lets say at -9999 z-index ? Iv tried a few things and non work.

tried:

Everything tired i placed in .css("HERE")

"z-index", -9999

"z-index", "-9999"

zindex, -'9999'

any idea's ?

thanks in advance!