ul navigation menu resizes in firefox Help!

[jevic]

I am having a bit of trouble with the navigation menu on the sample website I am currently creating. The menu fits perfectly when firefox is fully sized but when I resize the browser the menu always moves. For example the last li always moves down.

This is the css:
ul#navigation {
padding: 0;
margin: 0;
background-color: black;
color: #fff;
float: center;
width: 100%;
}
ul#navigation li { display: inline; }
ul#navigation li a {
padding: .25em 3.583em;
background-color: silver;
color: black;
text-decoration: blink;
float: center
;
border-bottom: solid 10px black;
border-top: solid 10px black;
border-right: solid 10px black;
border-left: solid 10px black;
}
a:link, a:visited { color: #008080; }
ul#navigation li a:hover {
color: white;
background-color: black;
} #header { position: absolute; top: 0px; left: 0px;
width: 100%; }

p.s

I realise this question is ask alot but none of the other answers help me with my problem.

[TheServant]

This prob won't solve your prob, but float: center is not CSS. There is only left or right.

Can you post your relevant HTML as well please.