Anyway, my browser start page is suddenly changed to mysearch-engine.net without asking. I always get new commercial windows when I want to open new tabs or access websites. Besides, the computer slags at times. I Google it on the Windows computer and find posts like describes it as a browser hijacker. It could endanger my private data!!! I follow support.apple.com for main page settings but failed still. To be honest, I have no idea now! Could you please help? Thanks in advance!