I see you have found a solution.

I also notice the wee space to the left and right of the menu bar, which is due to every browser having its own margin/padding built in. If you want to get rid of that, and have the menu really go wall to wall, insert this at the top of your style sheet:
body {
margin: 0; }
And if you want to center your menu, change this in the css:
#navigation ul
{margin:auto; padding:8px;
width: 490px;
}
The 490px width comes from the width of the actual menu. So if you add a menu item (or subtract one), you will have to change the width accordingly. I usually add a temporary border: border: 1px solid red; or something, in order to better see what I'm doing.
A further hint would be to change the colour of the active and hover states of the links to something that is visible against the dark blue background.