CSS菜单在firefox中落后

问题描述：

我正在现有网站上修复菜单问题。

该网站是 http://vipeduc.net/mgt/index.php [ ^ ]

问题是，当我们使用firefox时，菜单会落后于内容。

我尝试了很多，但我不能。

有人可以帮我找一下这背后的问题吗？

问候

Hi,

I am working on an existing website to fix the menu problem.
The website is this http://vipeduc.net/mgt/index.php[^]

The problem is, when we are using firefox, the menu goes behind the content.
I tried lot, But I can't.
Can anybody please help me to find what is the problem behind this ?

regards