Google Android dev team informs that "Starting in a few weeks, we'll be showing content ratings for all applications on Android Market. This new capability will provide users with additional information to help them select the best apps for them.
Android Market's content policy remains the same as before: apps will be rated according to four content rating levels: All, Pre-teen, Teen, & Mature. Details on the rating levels can be found at Android Market Help Center.
Starting next week, developers submitting new or updated apps will be required to include a rating for all apps and games uploaded onto Android Market. In addition, developers will have next several weeks to add a rating to existing apps and games. Once content rating is visible to users, any apps or games that don't include a rating will be treated as "Mature"."