HTML trouble (IE to FF)

[bigtimecow]

so i'm designing this webpage for my school's robotics lab, and i'm having a bit of a problem.

http://bigtimecow.250free.com/uml/index.html

this is the top menu, and when you view this in firefox it looks just dandy, no space between images, everything looks fine.
but when i view it in internet explorer there is space in between the rows and i just can't understand why!