Changing the width of the "Recent Online" widget

Hi,

On my forum (http://gunsnroses.lefora.com/forum/) I've increased the width of the sidebar to 400px to accommodate some of the widgets I have which I couldn't fit in the standard sidebar width. Now I would like to increase the size of some of the Lefora widgets to fit into the wider sidebar. I've been trying to do this with the "Recent Online" widget. I can find the correct code with Firebug and change it withing Firebug and everything looks nice. Instead of showing the avatars in a 3x3 grid that takes up much vertical space, the avatars are re-arranged on only two lines. But when pasting the CSS code it just doesn't change! So I figure the CSS code for this widget must be placed somewhere special within the overall CSS form, but where? Is the order of CSS code snippets in the overall CSS form important? Must this CSS snippet (element.style) be positioned somewhere special for it to take effect?