you need to specify the font name in quotes as there is a space in the name.
ie: font-family: 'trajan pro';
If that doesn't work, how is the trajan pro webfont being included? are you using a service such as typekit or a webfont kit as part of the theme or included via a plugin?
If you are not using a webfont, then that is the problem - as any font needs to be available to the browser for the browser to use it.