I just took a look. Do you mean those couple of pixels extra (on the right I think)?? The mathematics of the issue (quite apart from IE often showing things up differently) are against us.
Write the words of your menu in a line. Add 10 pixels on each side. This obviously means that in some places there are 20 pixels and in others only 10. Then think that a specific space has been reserved for a word in the layout of the horizontal bar. Then think that each of the words is a slightly different length... and hey presto! You have all the ingredients for asymmetric! The harsh reality is that it is difficult to get all the browsers to agree on how things should look... and particularly difficult to get IE to agree, so we designers are destined to make major compromises and just hope that things look "reasonably" right across all browsers.

ps. aligning your text to left or right will also influence how the finished product looks of course.