Excel Web app and Fonts

Currently there is no way to upload fonts into the web apps.

There are however small exceptions and work-around. Please see below article for more detailed information.

http://answers.microsoft.com/en-us/msoffice/forum/msoffice_word-mso_other/how-to-install-additional-fonts-in-office-web-apps/da5d5ac8-4820-4e01-a303-4b5858c5f20e