Greg's wife has an iMac running El Capitan, but now the Safari app just goes to Yahoo Safefinder no matter what! Rich says that there's some malware on the browser, likely an extension. Rich recommends Malwarebytes, and give the iMac a scan. Also, go through the apps and see if there are any that are unrecognizable. CleanMyMac is a program that can also clear out malware. Greg can also look for a browser reset in the settings, which will wipe out everything and start over.