Editing CSS of Submenu

Hi Sakin, I have just added a Gallery submenu and it doesn't look nice at all, see here: http://cinnamonearth.com I kind of aligned the submenu boxes with the Gallery in Firefox but it looks very different in Safari. Also, there seems to be an "invisible" border that you can see on the right side. What code would I need to get the submenu boxes the same size as their menu boxes. If possible, I think I would actually prefer a horizontal submenu but I did some research yesterday and if I'm not mistaken, that's not possible with my theme. I hope you got some advice for me. Thanks a billion, Jackie