Error: 400 Bad Request

Sorry, the requested URL 'https://snippets.mozilla.com/%C3%9DARTPAGE_VERSION%C3%BFirefox-1409201/%C3%BERSION%C3%A5APPBUILDID%C3%A5BUILD_TARGET%C3%A5LOCALE%C3%A5CHANNEL%C3%A5OS_VERSION%C3%A5DISTRIBUTION%C3%A5DISTRIBUTION_VERSION%25/' caused an error:

Invalid path string. Expected UTF-8