spacing between li's?

Hello: got a situation I cant figure out so I hope somebody can help…

here is the page: http://gerardsites.com/1a-test-ul/

basically i am setting up a ul list with pictures as backgrounds; I am going to have them in a row…

for some reason there is some space between each li element…I cannot figure out where it is coming from; I have the li’s set to “float: left” and if I remove that; when they go to a vertical list there is not space in between; i could probably get rid of it by putting on a negative margin on the li’s – but I would rather do it the “right way” by knowing where this spacing is coming from (and either eliminating it or changing it)…

thanks so much, G