virtual coin toss 55%

I was surfing the internet today and found a site that offered a coin toss game in PHP. The site claimed that it used the latest and most random computer algorithms to do the Coin Toss. In the next line it said that you (the player) would win 45% of the time. I would like opinions how somebody could offer a 50/50 coin toss game and gurantee a 45% win ratio for the player The idea of game programming is appealing, but I have no idea how you would gurantee that the player wins 45% of the time and the operators win 55% of the time. Thanks in advance Randy