Guys I've done some looking and tried a lot of stuff. Changing DNS servers ect but my iMacs Internet connection is horrible. I can't even load a YouTube video. The wifi works fine on my iPhone iPad ect. My fathers computer is fine it's the main mac running the modem/router through Ethernet connection and has no issues. It's seems to be only mine. It says I have full bars of signal and only started doing this today. I need some help please. Any other ideas of what could be causing this.