What are all the free online game websites

There are many, many online game websites and so its best to first decide which kinds of games you want to play. Its probably pretty much impossible to make a list of ALL the online game websites (free ones), because there are so many.
Go to Google and type in Free Online (whatever type of online games you like to play) Games.
For example:
Free Online Harry Potter Games
Then just pick a site and PLAY!