Line 252 of the source code shows the embedded javascript. 
The viewer can be opened in a new window, with the size and position set using the width, height, top and left parameters so the code looks something like:

onclick="window.open(this.href, '', 'resizable=no,status=no,location=no, width=800, top=100, left=100, height=600, toolbar=no,menubar=no,fullscreen=no,scrollbars=no,dependent=no'); return false;"

There is an issue with how the various browsers deal with size of the viewer and whether it opens in a new window or not. As follows:

As the page is on the lab web site:

On the Mac:

- in Safari if you click it opens in a new tab, but if you right-click the thumbnail and select > "open link in new window" the viewer opens in a new window which is appropriately sized to the image.
- in Chrome and Firefox, if you just click on it or right click >New WIndow it opens in a new window the same size as the parent window.

If I add in the parameters to the Javascript as suggested:

- in Safari the same happens if you just click it opens in a new tab of the same size as the existing, if you right click you get the window sized to the parameters .
- in Chrome and Firefox, clicking opens a new window sized according to the parameters.

If I add '_blank', into the javascript (without parameters):

- Safari still opens it in a new tag or if right-clicked in a suitably resized window
- in Chrome and Firefox it opens a new window but the size of the parent window.

In Windows 7 both IE9 and Firefox do the same as Firefox on the Mac.

We are looking at what to do to improve the uniformity of action across browsers.