thanks for your help Jason.
I tried creating a simple menu in css menuwriter and coding the css as you suggested, and have made progress.
The menu will look fine if I want the images to appear below the menu on rollover, but I can't get the menu to appear as i want if the images are to appear above it.
i tried assigning a negative margin to my tag, but this pushes up the whole of the li element
attached is a page with the css embedded, so hopefully you can see the issue, - the first link shows the image below the menu on hover, the next links show the image with increasing levels of negative margin.
eg
ul#cssmw1 > li#reviews1:hover > a:link {
height: 200px;
outline-style: none;
background-image: url(CSSMenuWriter/images/image.png);
border-bottom: none;
background-repeat: no-repeat;
margin-top: -200px;
}