Grails 2.3 changes css font-face url to "resource:/..."

A better solution I think is proposed by dmahapatro at: https://stackoverflow.com/a/22849288/2286664

You need to ensure your font files are known to the Resources plugin.

The following worked for me in my Config.groovy, adapt it based on your paths:

grails.resources.adhoc.includes = [
    '/images/**', '/css/**', '/js/**', '/img/**', '/fonts/**'
]

You'll needed to run grails clean after making this change.

The solution was to disable CSS processing in Config.groovy:

grails.resources.rewrite.css = false

I found the tip how to do that on the Grails mailing list.