Search.watchtelevisiononlinetab.com is a browser hijacker that will attempt to commandeer your browser search and homepage. The browser hijacker will send you to malicious websites to get money from you or infect your computer further. It may also prevent you from changing your settings back.
The browser hijacker causing redirects to search.watchtelevisiononlinetab.com is usually installed through bundled software without you knowing. In this case, it is the Watch Television Online browser extension. You have to remove it immediately.