I've found using the Google Chrome Page Speed plugin to minify my CSS helps avoid issues like this. It doesn't minify CSS as extremely as some other programs do, but I never run into browser rendering issues either.
I currently have a few stylesheets with @font-face in them minified using this approach:
- Download and install Google Chrome, if you don’t already have it.
- Install the Page Speed add-on.
- In Google Chrome, run the Developer Tools and click on the “Page Speed” tab. Then click “Analyze.” You’ll be given an overall score, and a list of things you can do to improve your score.
- One of the items on the list will be “Minify CSS.” Click it. Under “Suggestions for this page” is a link to “see optimized content.” Follow that to get a minified version of your CSS provided by Google.
Source: http://gomakethings.com/how-to-trick-out-the-performance-of-your-wordpress-site/