I am trying to display some text exactly the same in all browsers.
I\'m using helvetica, which they all support.
I\'ve found (the hard way) that each browser
all browsers "support" helvetica? which browsers do you speak of? there are a plethora of browsers listed here http://blog.mhurrell.co.uk/post/2946358183/updating-the-helvetica-font-stack that don't or at least cannot utilize helvetica. unless you are serving up a licensed version of helvetica to them. i'm assuming that you aren't.
that link is about building a better font-stack for cross-browser/platform helvetica...although that's a mighty big stack and you may not need it all. you can find others, read more:
http://css-tricks.com/snippets/css/better-helvetica/
http://www.awayback.com/revised-font-stack/
http://unitinteractive.com/blog/2008/06/26/better-css-font-stacks/