font-family: Comic Sans MS;
@a1jesin - Here on WordPress.com, fonts can be changed via the available fonts in the Custom Design upgrade, which the user has indicated they purchased.
@roxannesgalpin - Here's how to changes the Custom Fonts: http://en.support.wordpress.com/custom-design/custom-fonts/
If that isn't working for you (I see Museo Sans for your body font), try logging out of WordPress.com, clearing your browser cache and cookies, shutting your browser, open and log back in.
I do know that there is a glitch with Custom Fonts not "sticking" if you make another change somewhere else. If that is your experience, please let me know and I will tag this for Staff assistance.