Still need help. Thanks

Just a few days, I suddenly could not open my yahoo, webexcange e-mail account, windows messenger, as well as other important websites, like Scottrade, Fidelity, my bank account. The computer said that the pages I searched for could not display. I have try to use LAN setting, clean coche and other technicals. All of them did not work. Is anyone can help me to solve this problem? Thank you first.