since your design is 1000 pixels, and you have 7 menu items, you are not going to be able to come up with a menu width that will be exactly 1000 pixels:
1000 / 7 = 142.85
The best width you can come up with is 142:
142 * 7 = 994px
Try setting the background color of the topnav div to "#4870AA"
also the menu is outside of the topnav div. Move it inside of the topnav div instead.