evenly space thumbnails across a div

hi there,

in css is there a way to evenly distribute images across a page so that the left and right margins are equal?

i have two pages where there are sets of thumbnails controlled by the same css: one set is seven across and one set in four across. they are 100×100 pixels and the width that they span across is different. is there some way to make them evenly distribute and have the left and right margins equal?