popbox.js issue with img hiding behinde my nav menu question

popbox.js issue with img hiding behinde my nav menu question

I really like the popbox.js http://www001.upp.so-net.ne.jp/www2014/ and I have it in my website here http://www.toolbin.com/template5.shtml
My issue is that when you click the 1st tall image on that page it hides behind my nav menu. Is there a way I can edit your popbox.js file to make the pop image appear in front of my nav menu? Any ideas or suggestions and much appreciated and I thank you in advance
http://www001.upp.so-net.ne.jp/www2014/