jQuery hide/show <div> element appearing behind image

I have a div with a height of 35 pixels and a hidden div with a height of 200 pixels. I have a jQuery function which hides the smaller div and shows the larger div when clicked. This all works fine.

The problem is, when the larger appears it is behind an image which is below开发者_如何学C it. I have set the z-index of all affected object to no avail.

Any ideas how I can get this back?

TIA

Added position:relative to the div's and all was well in the world!