Another indication of a reputable Sweden betting sites is that they will say they belonging to the Nevada gambling association. Gambling sites are legal only if they are owned by a casino. The site is probably fake if they make no such claim. Also, if there is no affiliation with a casino mentioned, it is probably a fake web site out to get some money. If a site does mention a casino, call the casino and ask if it is one of their sites. This is a good way to check to see if the site is real.
Never give out personal information such as a social security number or bank account number on any website that claims they need it. Always pay using a transfer service, try not to use a credit card. Fraudulent companies will sell information once they receive it and could lead to identity theft. If a site just does not seem legitimate, trust those instincts and leave the site. There are plenty of other sites to place a bet with.