It means that the network is slow. The browser is smart enough to detect that the network is slow based on the time it takes to load your webpage. It is replacing the web font with a local fallback. The text rendered with a web font will not be visible until the font is downloaded.
You can fix this issue by following these steps:
- Update your browser to the latest version
- Disable AdBlock Plus extension for Google chrome
Also, follow the instructions provided by @Max Yudin in the comments.