How to use if in applescript

Hi i am making a game application in applescript. But when i was done it said this "Expected end of line but found ":".". The code i used was

`display alert "By taping ok you accept the following rules: Do not hack, do not cheat, edit komponents or download our site to your desktop! If you do not follow these rules you could get banned"

if {button returned:"OK"}
tell application "/Applications/Safari.app"
open location http://ift.tt/1YQ6vku 
end tell`

Can anyone help?