iphone 4s infection?

received a text msg from trusted friend. clicked on the link it contained. oddly, got a weight loss web site. (odd because we're skinny.) when i looked back at the 'history' to double check the sender, the msg wasn't there. called her, and she didn't send this text. at the time the phone was recharging on iMac USB port. i disconnected it and powered it down?

have i an infected phone? iMac? what should i do?