Browsergame Music
Online gaming, whether for serious gamers or more casual users, is very popular. Almost all games have soundtracks. Some games have large amounts of music recorded exclusively for them, and some may just license existing music. Some games do not have music but have sound effects which play when you click a certain button or do a certain action. These soundtracks, like almost everything else on the internet, are likely to be copyrighted. Even if there is not an explicit copyright notice with them, they may still be copyrighted. Federal law says that an author automatically has copyright on a work as soon as they create it.
If you want to use or download soundtracks outside of the game, you will need either explicit permission in the game saying that they are freely licensed, or you will need to contact the author and ask for permission to use it. Some of the larger games which have custom soundtracks have released their soundtracks for sale and can be purchased anywhere you would normally buy music. If you are looking for music to use in a game you are creating, you will need to either license or commission custom music, or use freely available music, which often requires that you attribute the author. Make sure to be clear on what the license is on the music that you are using.