firstly there is no such thing as a 'css' font. You use css to tell a browser to render text in a particular font if that font exists on the user's machine. Could you post the css + html?
First off, you may be interested to read this: http://www.ms-studio.com/articles.html
Arial is just a shameless copy of "Helvetica".
(So clearly, that will look just as good, or better.)
Though, I personally like to use Verdana as a clear, sans-serif fonts. It's not dissimilar to Arial.
