Help with css stylesheet

hey, i have recently made a site http://asktheangels.t35.com and it works fine with opera and i.e but when i asked my friend to look at it on firefox it went all messy, i then downloaded firefox to see if i had the same problem which i did, i dont understand why it just completly ignores the stylesheet.css and the php pages go all horrible looking i just wanna know how i can solve this problem and make firefox read the css file, could anyone please help me out here any reply would be apricated
Thanks