Help centering a div with a min-height

I’m working on https://www.deirdre-edwards.co.uk/index.php and have added a min-height hack to make sure that my faux column gif is repeated to the bottom of my ‘container’ div.

The container div should be centered horizontally, but the min-height hack (https://www.alistapart.com/articles/footers) only seems to work when I add ‘float: left;’

Can anyone help?

Cheers!

#container {
float: left;
text-align: center;
position: relative;
align: center;
min-height: 100%;
height: 100%;
voice-family: ""}"";
voice-family: inherit;
height: auto;
background: #FFF url(https://www.deirdre-edwards.co.uk/wp-content/themes/dufus/images/backstrip.gif) repeat-y 50% 0;
margin: 0 auto 20px auto;
}

(Strangely for once it looks how I want it in IE6 and not in Firefox!)