Top Online casinos are the Online casinos that make the most money because they have so many visitors coming to their site and gambling on their site. How does a site become a top site? First of all, location of the online casino might matter so USA online casinos might do better than ones that are from more unknown places. The popularity can depend on how the casino was marketed since you can notice that there are a lot of gambling sites ads all over the internet because they are in such high competition with one an another.