Tables exported from Photoshop were born with that problem.
You have two choices, go to the code and double check the size of every table cell and image inside of it or…
Create your site in a different way. You can use a single background image in your div. Deleting all the images from your table slices.
You can export the menu slices again, but without the background. Transparent gifs will do the job. Placing them again.
Anyway, no single straightforward solution for the problem. At least not one that I know.
I hope this helps
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