CSS Font changing | theme Twenty Ten

I have been working on it from whole morning, but i couldn’t resolve it.
I wanted to change the fonts of my website.
the embeded theme putted by css was
>Georgia, “Bitstream Charter”, serif
>”Helvetica Neue”, Arial, Helvetica, “Nimbus Sans L”, sans-serif

in style.css file.
i was trying using the Dashboard editor.
but its not working.
the file updated but no change on the site.
i was searching here for a solution.
but dont have much time…
can anyone help me out?