Site looks worse in IE 8

[Mir]

My Javascript menus have odd marks on them in IE 8 -- little boxes between
the parent items.
I admit, these same marks appeared in Mozilla all along, but I ignored them
because in my part of the world almost all my viewers use IE (as my usage
reports confirm).
How do I find out exactly what is wrong and how to correct it?

 

[Mir]

Thanks, Tom, I'll do that.
The real world! I was already kicking and screaming about leaving the pretty
protective bubble of FrontPage, now this!