simple css layout gone grey!

For once IE's fine!,
but........I cannot get rid of this annoying little grey box in mozilla,
I'm hoping someone will point out my mistake?,also i cannot get
moz to top align my css boxes?, thankyou so very much! :thumbsup:

all the css and html are in one html doc within zip file.

The grey background is being set in #mainnav div.
Just remove the line highlighted below.

#mainnav{
width: 650px;
height: 20px;
margin-top: 20px;
float: center;
background: #C0C0C0;
}

you can never see them yourself can u!

cheers! I really appreciate it! :thumbsup:

in the mainnav div, it was aligned center not left!, its also sorted out my top margin problem!

cheers :thumbsup: