can;t sign out of mail box, to sign on other help button not work nothing on top, can;t delite mails as delite button not work what is this can any one help>thank you

I can't sign out of yahoo mail adress to sign on new one as the existing one still open, can;t delite mails as delite  button not work, can;t click nothing, and is same to hotmail adress too.Same problem.Been scanned the computer, updating , and pluggings as is sey some pluggins from this page missing wonder what is?as can;t click nothing, and nothing have no idea what can be.Can any one help me? is so weird all this.Thank you