need help centering CSS popup image

[Arkaein]

Hi everyone, I have kind of a tricky problem. I'm trying to build a front page of a website which has several links to subsections of the site. I want these links to be artfully arranged in an approximate circle on the screen. Each link is positioned using a combination of a common style defining absolute positioning and local styles defining the actual positions.

The popup images appear all right, but I have so far only been able to specify the position of the upper left corner. I have been able to center the image by specifying right and bottom along with left and top, but this makes the image stretched and resized when I only want the position to be fluid.

I've tried playing around with things like margin: 0 auto, and text-align: center, but have had no luck. Anyone know of a solution? It would be best (i.e. most elegant) if it did not require the CSS to "know" the size of the image, but I'll take any solution using pure CSS layout.

A related but less important issue: I've had to use fixed rather than absolute positioning because any absolute positioning I try is relative to the parent <a> box. Is there any way to skip to a higher level in the box model to use absolute positioning relative to the entire window?

Thanks.

Relevant CSS:

a.page 
{ 
 font-size: 1.5em; 
 position: absolute; 
} 
div#content a img 
{ 
 position: fixed; 
 border-width: 0; 
 top: 50%; 
 left: 50%; 
 visibility: hidden; 
} 
div#content a:hover img 
{ 
 visibility: visible; 
} 

Relevant XHTML (most links removed):

<div id="content"> 
<a href="liquid.xhtml" class="page" style="top: 20%; left: 55%"> Liquid<img src="images/water.jpg" /></a> 
<a href="puzzle.xhtml" class="page" style="top: 50%; left: 10%">Puzzles<img src="images/jigsaw2.jpg" /></a> 
</div> 

[Arkaein]

One more thing I forgot to mention: it would also be nice if the text of the absolutely positioned links was center aligned. This isn't a big deal because each link is positioned individually, but would improve the positioning of the links if unusually large fonts (or small browser windows) are used.

text-align: center doesn't seem to do any good, either for the links themselves or the parent div.